More DPS is always needed for roulettes
For dungeons you need 2 DPS compared to 1 tank and 1 healer
For trials/raids you need 4 DPS compared to 2 tanks and 2 healers
For alliance raids you need 5 DPS compared to 2 healers and 1 tank.

If healers and tanks were considered well designed and fun why do DPS queues take upwards of 10-20 minutes on average when you need more DPS to fill up parties than the supports?
Clearly it's because there are less people playing them. Why are less people playing them? Because DPS is more fun.