The simplicity of the game is a large part of the problem in my opinion, take the healer DPS issue as an example. The problem we have is if they don't need to cure then they either stand there and do nothing or DPS. Throw in that they can do good DPS and pressure gets put on people to fullfil a role they feel they didn't sign up for. If the healer had something else to do, such as put buffs on players or debuffs on mobs then they would be busy enough, and contributing enough without needing to DPS. Haste and Refresh from FF11 are perfect examples of this.

I'd also like to throw the trinity concept out of the window to an extent and include the 4th class, support. If all dungeons where for 8 players not 4 and one role was reserved for a true support class (what BRD should have been imo) then it would help to get out of the situation we have now where everyone is similar in DPS output.

In my opinion the game should focus more on the buffing/debuffing meta game if we are to get away from the DPS mentality that people find so frustrating.