Others like Signet of Air are nice, but the gap closers you already have should make it mostly redundant. Cleansing Fire can also be a nice pick up if you get sick of some of the enemy conditions, and it applies burning which can combo nicely with Fire Grab for extra damage. But I would use your utilities to flesh out how survivable you want to be. Large groups typically make worrying about death a mute point, but keeping some stun breaks handy may be worth your time. They lack a lot of the gap closers some other classes have, but they can get high swiftness uptime to make up for it. We would love the opportunity to be your provider of quality SWTOR Credits. That said, you still have plenty of options to improve your RC output and get those mob kills to count. Any of the Engineer’s main weapons really fail to do the job compared to some of the kits. If you forced me to choose, I would say Rifle, but that’s just because Jump Shot is a decent gap closer and Blunderbuss is passable.
Below is a breakdown, by profession, of ways you can help improve your RC output. They really do drop the shiniest of loot. The choice of weapon here is easy. You want to focus on multiple target damage that isn’t condition based. The high mobility and gap closers of this weapon combination helps you stay in the fight more often, and ensures you get to the fight before it’s over. Spend most of your time in Fire, although you may find starting a fight in Air isn’t a bad bet. It gets you in range and does AOE damage. A trick with spells like Drake’s Breath is make sure auto targeting is off, and then you can sweep the camera side to side and the spell will move with your view. Stay on the edge of the mob groups, this way you can maximize the number of enemies in your conal attacks. Between conal attacks, your Fire attunement auto attack will suffice. If you want you can hop to earth and cast Earthquake, but that’s unnecessary. The only utility skill I feel is a must have is Arcane Wave since it gives you one more AOE direct damage spell.
Both of those are too high of a cool down to be useful in drawn out skirmishes however. Flame Blast is good for the same reason Napalm is, you can fire it at enemies that are not directly by you to get some RC while you focus on another group. I tend to use this off cool down since it has a pretty low cast time and puts out good damage in a fairly large radius. If you choose to run Grenade Kit you can get by. The vanilla Grenade attack is typically fine, but some of the other attacks actually have larger radius, so in cases where the enemies are a little less tightly packed, they tend to be better. It’s not a complicated kit to play, and provides a nice mental break to torching everything down with Flamethrower. As for other utilities besides kits, Elixir B is a must have. If the fighting will be in one location for a long period of time, Rocket or Rifle Turret isn’t bad either. But if you are on some sort of escort mission, leave the turrets behind.