Like many other said already, people have different standards by which the give out commendations.
Personally, I don't commend healers just for healing and dpsing because i expect them to do that anyway if they have the leeway (which you obviously had, since everything went smooth).
I commend healers when they save us from a dangerous situation or get us through anything that would have normally killed the group with just an average healer.
If no such situation pops up because everyone else isn't messing up either, bad luck, but you just didn't get a chance to shine, sorry.
Also, quite often, people don't bother giving out commendations at all and just leave the content instantly after loot is distributed. It sucks, especially if you went out of your way to maximize your own performance, but in the end, you'll just have to deal with it.
