I guess you have to make a choice between adding some skills from either the Nades, or the Marksman tree [imo, not possible to get anything useful from both, given that you've invested a lot of points in Tinker]
You don't say where your skill points have gone, but given that you are summoning, I'm guessing that you'll have a lot in wizdon rather than dexterity.
That being the case, I'd suggest looking at the nades tree.
If you have enough points, Body of Steel is a useful survival skill [can't remember what it's stats are here, but the defence buff when maxed on RU is quite high]
Sticking with the Tinker tree, you have Medical widgets and Supression widgets, the latter ideally should be maxed for best benefit.
Personally, I'd re-spec out of the teslas, into something with a bit more damage, or one of the buff widgets as above.