TL;DR at the very bottom!
I played as a Pyrotech in PvP all through Beta, but I decided to switch to Assault Spec Vanguard in EA (they are the exact same thing). It's a very fun AC, but how it plays depends entirely on you.
It's strengths:
1) Flexibility - good mix of both melee and ranged abilities
2) Peels - spam Flameburst/Rapid shots to proc slow + 2 taunts + Grapple
3) Burst Potential - The more Flame Bursts/Rocket Punches you cast, the more likely it is that you will proc a free Rail Shot that will also dissipate 8 heat, which leads you to more Flame Bursts, which leads you to more . . . you get the idea. Going balls to the walls during Explosive Fuel (25% extra crit chance) while also using Vent Heat + Thermal Sensor Override can lead to some pretty silly amounts of damage.
It's weaknesses:
1) Not tanky - you won't really have any super awesome abilities that allows you to keep spamming damage while being focused. Energy shield is great, but it doesn't really keep you alive if you get focused. Sure, you have talents that allow your defensive CDs to be come back up much faster, but defensive CDs aren't measured by the number of times you can use it per match, but rather how many times it actually saves your life.
2) Easily Kited - you don't have any gap closers other than Grapple. In fact, you are the only melee with only one gap closer and no other way of increasing your speed. Your slow isn't as great as Sith Warrior's free AoE slow, and it's short duration means that any type of CC/bad luck with procs means that your opponent will not be slowed.
3) Bad Heat Dissipation - you will have to use your Rapid Shots a lot more than with Advanced Prototype. Your heat dissipation talents are all random, so you often have to do some on the fly math to make sure you don't go over your most efficient heat threshold.
That said, if a Pyrotech is played right, none of these weaknesses really come into play. You don't have to be tanky since you can always engage on your terms. Always position yourself so that the other team can't effectively switch to you, ever.
Kiting you is a matter of interpretation, since your range is completely dynamic. If Rocket Punch is about to come off CD, you want to be in melee range. If you have the spare heat to spam Flame Burst, then you want to be within 10 meters. If none of these two things are true, you are free to sit at 30 meters.
Bad Heat Dissipation only matters if you actually care about having a super smooth rotation. As long as you are able to kill your target during your burst, then what heat you end up at really doesn't matter.
:wea_02:TL;DR - Pyrotech Powertech is an extremely fun class in PvP. However, it is not a "brute force" class that will allow you to spam abilities and win. The differences between being a good Pyro and a bad Pyro are extremely subtle, and entirely based on the player.