I've thought this before but the problem is commendations are unfair and always go to the healer or tank it seems. When I play as DPS I pretty much get none, only once in awhile. WHM is my main, and I'm always getting at least 3+ each run of an 8 person one, usually 2 or so on a 4 person. Typically I'll give mine to some random DPS since I know they don't get many. It's not that DPS aren't valuable, it's more that it's hard to see when a DPS does something that really helps everyone out, where most people seem to just think "well we made it through this, must have been the healer keeping us alive" type thing.