Mass Effect 3.7: "That was for Thane"

[Tome]

Engineer. So far I've maxed out the sentry mine ability(if that's the name), and it seems pretty effective. I was planning on ignoring proximity mine with him and running shield boost and that along with the two bottom skill trees, but I've never played an engineer competently before, maybe I'd be better off running it as a caster.

He is only level 11 at the moment, as I am terrible and have only played an engineer once.

Proximity Mine is very good, I'd advise against skipping it. Particularly the rank 5 evolution that debuffs enemies (*hint* which stacks with the same effect on Recon Mine *hint*). It also has a much shorter cooldown than Recon Mine, making it better for using offensively.

The skill you can safely skip on the Volus is Fitness. With how fragile they are it doesn't really make much difference. Cloak and Shield Boost are what keeps a Volus alive - which is another reason why using Recon Mine for your offence is a bad idea, the long cooldown leaves you vulnerable when you can't use Shield Boost.

I use a 6/6/6/6/0 setup myself, but 6/6/6/5/3 is also good. Bring a decent lightweight gun, throw your Recon Mine into whatever area is going to be your killzone and then use Proxy Mine and Shield Boost to support your team (also, remember to shoot things a bit in between powers).