DPS blames Tank (if they lose Enmity/pulling too much) and Healers (if anyone dies while the healer still has MP)
Tank blames DPS (if mobs stay alive so long they run out of CDs/messing up mechanics) and Healers (if they go down and the Healer still has MP)
Healer blames Tank (for not using enough CDs/pulling too much) or DPS (if the enemy lives so long the Healer runs out of MP/getting hit by AOEs)

Literally everyone blames everyone else, when it's usually a combination. DPS forgets a mechanic or eat an AOE trying to eek out damage, Tank is a little overzealous with pulling enemies while with undergeared/inexperienced DPS and/or Healer. Healer stays in Cleric Stance too long or doesn't compensate for Tank/DPS mistakes. The best players are able to objectively review their own play and point out their own mistakes.

I know as a DRG I am well aware that if we do big pulls back-to-back in the Expert Roulette dungeons (I'm not super well geared yet) I am going to run out of TP pretty quickly as I just don't have the damage yet due to gear limitations to kill quickly and keep up my AOE Rotation TP-wise. I let the Tank and Healer know so they can compensate. So far they have listened and understood, but I guarantee I'll run into a group someday soon that won't (or I'll get geared up enough that it's moot).