I'm an Assassin. Force Lightning is useless and should be removed. As a proof, I don't have it on my shortcuts. Proves I'm right, right?

The Empire collapsed both in the past and the future of the game in order to reinvent itself. In the game's iteration, not all Sith are inherently evil, depending on player choices but the same can be said about NPC Sith. Malgus was definitely trying to address the faults in the structure. Too bad he was on the wrong end of my lightsaber. There's one of the SI dialogs with Ashara where the player pretty much exposes her different ways of leading the Empire. One of them is summed up by bringing peace to the galaxy and restoring order regardless of the cost: efficiency before morale. Not all Sith, NPC included, kill everyone on a whim. Coercion and bullying are sometimes just as effective. When it's applied, it is sometimes in order to fit with the greater agenda of having a galaxy free of any conflict or corruption. Or maybe, just for the fun of it. Force shock hardly gets old Anyway Evil will triumph. Because Good is dumb.

Because you don't know how to use it effectively doesn't make it useless: high damage at zero cost. Weak and Silver mobs take a lot of damage from Tumult (and the electocute or shock you used to stun them). They'd end up dead all the same if you didn't use Tumult. It's faster and uses less ressources though. Use it on weak mobs that are gnawing on your healer(s). Use it on the sniper mobs that are way out of AOE. Or don't, but then don't complain that weak mobs need a nerf.

It may not be related to gear. Prioritizing your abilities is also important. Check out if you are using Wither and Discharge the moment their CD goes off. Same for Shock if you buffed it to the teeth (which should be the case). Your survival CDs don't generate threat. So if losing mobs is actually an issue you're going to need to prioritize aggro generation above survivability. Remember to pop your shield on the melee guy and not on the healer, who, most of the time, is out of the beneficial range anyway. Weak and silver mobs are rarely ever an issue if you lose them. If they're going for a ranged, chances are they'll drop dead before they reach them. If they go for the healer then Force Pull or Taunt them to buy time. Assume DPS know what they're doing. Chances are they do if they are attacking weak mobs first and dispose of them fast.

You don't need it as a Sorcerer. As an Assassin it is however pretty nice, especially following the buffed up version of shock Deception has. It goes Shock->Tumult->Dead. Of course stuff would end up dead just the same if you didn't use it. It's just faster because it does nice damage at no cost (save the CD of course). Since Force is something you want to preserve as a 'sin, a zero cost is most welcome.

Easy solution: CTRL. Or SHIFT. OR CTRL+SHIFT. You're welcome.

Mobs having extra range on stealth detection over that of their normal aggro range is already documented and indeed annoying. If they don't see you when you don't hide it's just illogical (and sometimes dangerous) that they detect you from further away if stealthed.

Still using it regularly enough in HM to get rid of weak mobs fast. It's generally Shock->Tumult->dead. Plus as it was mentionned, not costly to do. But yes, that's situationnal.

Xalek because he uses the exact same gear you do. It makes you capable of gearing up the both of you with more ease than a companion that uses Heavy Armor or Strength. You can swap roles and gear with him if you feel he's dead too fast and/or doesn't do enough damage. Ashara is sexier though. Just saying.

How exactly can you tell whatever your DPS is? Your Sniper may deal 5000 damage every 5 seconds. If your assassin does 1001 damage every second, he still outdamages your sniper. Sins have stealth. Stealth isn't the end all of abilities. It's quite useful but that's that. I understand you have some kind of imaginary class ideal you'd like to play. That assassins don't quite fit your dream class is nobody's fault though. Try operative or marauder, see if they're a better fitting match. As it plays currently, the class is a nice spell/melee hybrid with stealth as icing. It's entertaining to play the way it plays, quite challenging as well and very involved. Not everyone can love everything though, and it's quite all right if you don't.

Darkness and Deception use a lot of saber moves. Deception doesn't use Force Lightning under normal circumstances. I didn't get around to playing Madness but from the tree it seems to be the one that is the most spell oriented. Both for Darkness and Deception your melee strikes will influence how and when you use your spells. You will always use at least Shock. Try for yourself if you haven't. You're giving the impression to have read the guides without playing the game as sin and seeing how that actually works out with first hand experience. It's very fluid and if it's a concern you're going to be in melee range most of the time. Anyway we're really an hybrid of physical and force damage. Like a spellblade, a mage warrior or a red mage for reference to other games.

As a Sin it doesn't really matter: you swap gear with Xalek and/or use him as your alternate gear storage. If you don't, you should. Get him whichever role gear you're not doing: Survivor if you're specced Madness or Deception, Stalker if you're Darkness. When you feel like respeccing, grab his gear, put yours on him.

Games are a waste of time by definition. Unless you get paid to play them, but there's few that do. If what you enjoy is seeing a game played for you, the entertainment you're into is called television. This is what you're really enjoying. There's no shame saying "that thing's not for me". I'll go first: I don't enjoy fishing. It's a huge waste of time (too). That's why you're not going to catch me by a river with a pole.

If you change to the available DPS charge as a 31/0/10 specced assassin you trade your 150% armor and threat buffs for more damage. Some attacks specifically require you to be in Dark Charge, but they're the ones with the high aggro modifier which you won't be using in a DPS role anyway. Just so we're clear, even if you're in a DPS charge, you'll be dealing slightly less damage than if specced Madness or Deception as a Darkness assassin. If you have an enrage timer to meet, it can make it a subpar choice if you're not the one tanking.