I've received 5 commendations so far from around as many runs and I'm guessing that's mostly due to explaining strategies to first timers. The truth of the system, much like the additional rewards in the roulette system, is it's skewed in favour of tanks and healers. No one really ever says, "Well done" to a DD job but they feel a tank or healer who have simply done their job and not sucked are at the top of the pecking order when it comes to handing them out.