The general consensus from what I've read is that skill power levels are seriously screwed, and there's a lot of talk on the reddit that skills in general are pretty much pointless. I really haven't varied from the revive hive/healing chem launcher so I can't really speak much on that. I just hit WT1 this afternoon and the first two invaded missions were awesome fun. The AI on the Black Tusk guys is really a step up - and I know had I been facing that level of opposition when i was level 1, I may well have never made it through the game.
As to the build, I'm not to the point of having a *ton* of options yet. I've been using as much +damage to elites as I can roll, but I've been really happy also with Patience (after 3s in cover, repair 5% armor per second). When I was doing Roosevelt Island, I picked that talent up pretty early and it really made things a lot easier - especially when I also had the Preservation talent as well (killing an emeny repairs 5% armor over 3 seconds, more for headshot). The downside was that I didn't have any decent rifles for a while, so I actually went with an AR primary / LMG secondary for the first WT1 mission and it was definitely harder to pull off consistent headshot damage.
The bonus damage to elites has been a freaking godsend at times. Those MFs with the sledgehammers in particular, I can only successfully dodge so many times so being able to drop them a lot faster is outstanding. The one thing i want to try is the First Blood talent (from full mag, first shot into any part of the body does headshot damage), but it looks like you have to have an 8x or higher scope equipped so that may end up being something for fun.
