There is no debate. Thick skin is always better than OWLF trained if you only pick one. If you want to be a extra tanky assault, you could spend all your points on thick skin and OWLF trained, sure.
My point is I keep seeing FT randoms choosing OWLF trained alone. I feel that they must not know it only reduces damage by 5 percent.
Solution: add a description of what OWLF trained actually does, so new players can make an informed decision.

