For me, in pve, I make sure I know what level I'm on and know what buffs (txt a void dmg) or nerfs (juggler) the level has and act accordingly. I'm a hunter so I change my gunslinger specs also. For example today, I turned on chain of woe, key hole and the thing that gives me an xtra throwing knife if I kill something with an head shot. I calculate all that at the beginning of the mission in like 40 secs then I attack.