I usually commend DPS unless they weren't AoEing or not using their abilities, if the healer is DPSing and going all out though I'll commend them more but it's a toss up usually. And 90% of the time I'm tanking so I dont commend tanks unless I'm doing an 8 man trial or 24 man but usually I don't commend them unless they come shirk me or something its harder for tanks to stand out to me because they have to really do something to catch my interest since I'm a tank main.