If you're leveling still, I suggest don't use it til level 48. Because it requires high end talents on both trees. You'll be better using typical build like deep pyro. I completely agree with playing what you like. The OP was asking for other people input on what their builds are which is why I posted my spec and my playstyle (tanky mobile DPS up in your face build). ST/Pyro isn't the best PvP spec, but it is the best that fit my style.

As of right now, Ion Gas Cylinder is either bugged out or the tooltip is wrong. The damage currently is about 40% of the tooltip as a lot of other powertechs had confirmed. 40% of the tooltip should be ~200 damage for me. 25% of that is a whooping of 50 damage.

If you are deep shield tech build, a tank set may work better since you focus on maximizing your survivability. If you're ST hybrid into AP or Pyro, well it depends on your play style. As ST/Pyro, I use Eliminator set and focus on damage with the perks of being a tank (guarding and jet charge).

It has to be wasted to reach Superheated Rail. And no one is stupid enough to spec for Shield Vent and Flame shield then run with CGC.

Rocket Punch and somehow I'm stupid enough to spell it wrong as an acronym. DON'T JUDGE ME. This spec has a very high up time on targets leading to more damage overall instead of running around like chickens praying that you won't get knock off the ledge. Heat is not a problem for this spec. You'll be hitting RP* and Rail Shot every time its up and spam Flame Burst in between for more procs. Use Thermal Sensor Override for Incendiary Missile when you're running trouble with heat but need to put your dot up. If you want to slow and catch up to your target, use Rapid Shot since it's a pretty high chance to proc.

I just tried that spec literally 5 mins ago. Couldn't stand playing Huttball without Jet Charge. TD is stupidly crazy tho. I got a 4.2K crit TD and 3.7k rail shot burst with it. But I guess the spec isn't for me since I melt pretty easy.

I'm using the eliminator set. The two set bonus is worthless since it's only for merc. The 4th set bonus however is extremely powerful (15% crit boost on Rail Shot). This allows you to stack more surge and power instead of crit since your two major damage abilities have crit bonus (30% from talent for RB, 15% from set bonus for Rail Shot). It maybe a bug or a tool tip error. I use ion strictly for the shield chance, the slow, and the dot (others are just icing on the cake).

You mean 40k protection? ST/Pyro is the jack of all trades, master of none. However, it's that versatility that makes it good in PvP. I can guard/protect my teammates, pull up good damage, and survive quite long. I think my best match is like 400k damage/80k guard.

Here's the spec I use: http://www.torhead.com/skill-calc#301RRGbbMdoZ0MZbIbbdh.1 Emphasis on Rail Shot (and RB but more about Rail Shot), you can pull an impressive amount of damage for a tank hybrid while keeping the mobility and survivability. Yes, I'm using Ion Gas Cylinder to increase my shield chance (for survivability and talents like Flame Shield and Shield Vent). I'm using the DPS "Eliminator" set for the 15% chance to crit on Rail Shot. I will never see a 5k crit, but a 2.5k RB followed by a 3.5k Rail Shot is just as satisfying. Stacking Explosive Fuel with a Relic will give you massive amount of burst given decent luck.

This is all my opinions. For PvP, losing out TD is a big loss. TD + Rail Shot is the ultimate combo to kill healers if you catch them. You also lose 50% spammable snare. Sure, you'll make up for moving 15% faster, but that's not gonna help to close the gap as much (and Pyro already lack on the gap closer department). Think of it like a Ret pally of SWTOR if you played WoW, but without freedom and snare cleansing (vanilla/BC ret pallies). For PvE, since there's no parses and combat log. I'm not really sure about the heat gain will outweigh the loss of damage. Let's see: Loss of CGC dot damage. Loss of Burnout (3% crit and 30% more dot dmg on target below 30% hp) Loss of Intimidation on Shield Tech tree. Loss of TD (one of the best damage per heat on single target) This is based on a typical Pyro dps build: http://www.torhead.com/skill-calc#301bMZMsZfhMbdGhrs.1 In conclusion, I don't think the 8 heat will help you when you trade off so much. If you have heat problem, utilizing Thermal Sensor Override and Vent Heat (Pyro has talents that lower the cd on both) will have a much better effect than an 8 heat/sec.

First and foremost, what's the focus of the spec? PvP, PvE, solo, etc...

I would suggest leveling as Shield Tech with Mako out at early level. Since the other trees don't get their core talent til later, so the difference is negligible. You can stay Shield Tech all the way to 40, but by then the mobs already scale above your petty damage and you should switch over to AP/Pyro if you want faster leveling.

There's no "best" PvP build. It all depends on your play style. I am currently using the hybrid ST/Pyro. Gotta love the mobility with Jet Charge and the survivability. My damage is also not crappy comparing to deep Shield Tech build. I can turn a geared healer/tank inside out if he doesn't use his CDs or getting helped. And no, our damage is not lackluster comparing to merc. Go pyro with decent gears, and you'll nuke the other team down. Merc also doesn't possess close to the mobility that we have.

I think it means any attack has to do with your blaster? So Unload and Rapid Fire definitely proc it, and maybe Rail Shot (idk if its considered tech or range)

Hybrids are perfectly fined. I'm currently using the typical 21/2/18 ST/Pyro build for pvp with Eliminator set for the 15% crit chance on Rail Shot.

Combat Tech: 2p: Increase Carbonite duration by 0.5 seconds. Reduce the cd of Determination by 15 seconds. 4p: Increase Rocket Punch chance to crit by 15% Eliminator: 2p: Reduce Jet Boost cd by 5 sec 4p: Rail Shot crit increase by 15% Super Commando: 2p: Jet Charge cd reduce by 1.5 sec 4p: Increase dmg by 5% while guarding Your spec is a heavy ST build so probably going with Super Commando to maximize your survivability.

Currently using ST/Pyro at 50 with 8 pc of Champion gears, I can take a lot of damage while pushing out even more. I'm currently using the Eliminator DPS set for the 4pc 15% crit Rail Shot bonus. Grab a good healer and both of you guys can literally wipe the other team. In one Voidstar, I dealt 400k damage while having 80k protection (granted both of us were just trying to farm them). Popping Explosive Fuel + 355 power trinket make my Rail Shot crit upward to 3.5k and Rocket Punch around 2k-2.2k.

Shield Tech/Pyro hybrid has been posted around here: http://www.torhead.com/skill-calc#301hRGbbRboZ0MZbIbbdh.1 Currently using it at level 50 and topping both damage and protection regularly. Any variation from above will do.

Currently ST/Pyro 21/2/18 with DPS gears, spec feels amazing with survivability, mobility, and damage. However, now I'm having a new problem of which PvP set to pick: Combat Tech or Eliminator. Combat Tech has a good all around bonuses, but the 4pc of Eliminator comes with a 15% crit chance on Rail Shot (2 pc is worthless since it reduces Jet Boost). The 4 pc of Combat Tech gives 15% crit to RB, but I feel like it is overkill since I'm running around with 25% crit chance + shield vent talent.

There's an internal cooldown on both Flame Shield and Shield Vent so the loss is not that big of a deal.

I fully support Chainsawsammurai build. Currently using it at level 49. I focus on solo, PvP, and to a lesser extent of tanking and group DPS. In theory and my experience, this is a "jack of all trade, master of none" spec. You deal good DPS, can take some damage, and great mobility with Jet Charge but in no where close comparing to others which specialize into that particular aspect. It's really good for soloing. Ion Gas Cylinder is the choice here due to the 15% shield chance for Shield Vent and Flame Shield. Deals good amount of damage with Rail Shot spam (given good RNG). With Mako out, you should be able to solo just about anything including 2 men heroic quests. For FP and group dps, you'll have to switch to Combustible Gas since Ion gives massive threat boost. You won't be doing as much damage like you were soloing (loss of Shield Vent and Flame Shield). Good all around spec for PvP, I choose this spec because I love the PvP tanking of SWTOR. However, I want to be able to use Guard/Taunt while put out decent amount of damage. Keeping Jet Charge is just a bonus. This is for higher level since you need a lot of points to reach the high talents of both tree. But at level 50 and my last respec cost around 60k credits, I need a spec that can do both solo and PvP. For your level, you'll probably be better off with deep Shield Tech or until you have enough points to max Prototype Particle Accelerator for a pyro build.

This spec can be severely gimped on heat with bad procs. I'm using a Shield Tech/Pyro build similar to this for PvP and solo. You'll have to utilize Thermal Sensor Override and Vent Heat in case of bad RNG.

Is it me or torhead gone wrong since you didn't spec into Prototype Cylinder Ventilation for a High Energy Gas build?

Without the 15% shield chance from Ion Gas Cylinder, you will only have 7% chance on shielding the damage (unless you have shield rating gear, but why would you have tank gears?). So the two major abilities from Shield Tech won't get its full benefit (Shield Vent and Flame Shield). You'll probably be better spec into Puncture for a stronger Rail Shot. On another note, I possibly somehow saw that you spec into Ion Gas Cylinder. Edit: I also wants to know what's your focus on the spec. Is it solo, PvP, dps, etc...?

Which cylinder are you planning to use? If you pick Ion Gas Cylinder (hence the talents in it), all the points in Bursting Flame is wasted. I have a similar build however I went deeper into Shield Tech to take Jet Charge for mobility. Heat is not an issue with this spec since you gain benefit from both Shield Vent and Superheated Rail.