I read over a review @fineaid wrote after the BWE about the build he spent most of the weekend using. Coincidentally, we used a very similar build, although I went heavier on damage.
Having both the turret and the elixir gun gives you the ability to keep regeneration up on all of your friends. Three of your skills apply regeneration to your allies. Keep in mind that in GW2 regeneration stacks increase duration, not intensity, so stacking doesn't help us much as far as cooldown management goes.
- Healing Turret
- 20s recharge that begins when the turret is destroyed. In the beta the recharge seemed to start all over the board. Sometimes when I placed it, sometimes on destroy. There's some quirks to work out with turrets.
- Healing Mist
- 40s recharge: AoE's using the Engineer as the origin. Range seems smallish.
- Super Elixir
- 20s recharge: ground targeted Aoe, also leaves a combo light field
How to do it
Initially it seems like you just want to leave your turret down and use the other two skills to fill gaps. However, because the recharge starts (or is supposed to) when you pick up or destroy the turret, you actually want to build a rotation involving the turret. Why? Because you want the ability to be more mobile, ie. moving your turret. And also because dropping the turret is your biggest self heal and you want to use it as much as possible.
In the Wild
A fight might start with you dropping a turret to get regen on your group. Regen should refresh every ten seconds, so kill the turret at 10/11 seconds (you are a robot, right?). If you are in the backlines, lob a Super Elixir about 10 seconds later. This will leave regen up on the group but maximize your cooldowns. Now you have 10 seconds until your turret, but 8 seconds of regen left. (Traits can fix that gap btw).
This is where I would try to use Healing Mist. You have to be with your party for it to work though. But working its long cooldown into the rotation will alleviate some pressure on you since we aren't robots.
So there you see a regen rotation that looks like: Healing Turret Regen, Healing Turret Regen 2, Super Elixir, Healing Mist/Healing Turret, Repeat.
Note: All of the recharge times I listed are without traits. They can all be reduced with the use of traits.