2) Shockwave: Huh, good god, y'all. What is it good for? Do I put any points into it at all?
"Absolutely nothing. Say it again!"
I'm not normally too quick to jump in with build recommendations, but the BatSent is one of my favourite, and most used characters, and I haven't put any points in Shockwave for a very long time. Horrible power - the most anti-social thing in the whole game. If you're serious about playing him as a support class, I genuinely wouldn't spec into it, cos you'll probably be kicked from your next game. The only time I miss Shockwave is when I can't 'return the compliment' to a sniper teammate who repeatedly targets the mooks I'm winding up to decapitate.
I pretty much only ever use the Kishock on him (off-host, quite happily), but looking at your manifest I'd recommend either the Harrier or Crusader. He's the only kit other than the TGI that I would ever think of putting the Harrier on because of his great passives.
I understand the reluctance to get into CQC, but the Batarians' melee is one of the great powers. It's just immense, if a bit slow. Admittedly, the Soldier and Vanguard are even better, so it makes sense to spec the Sentinel as a pure tank, not forgetting that his Heavy Melee will still do 1600 damage even without enhancement beyond the basics from BA and Fitness. If you do go for a tank, Shield Power Cells give a 1.6 sec shield recharge delay - or 1.28 with Stronghold Package!!!
He was one of the first characters I regularly took into Gold, and while his DPS can be underwhelming, he's almost immortal. JIM!!!!!!