All MMORPGs suffer terribly with long dps queues for dungeon content. Raid content it's the other way round, tanks and healers find they have long raid queues or struggle to find companies where tanks and healers aren't already accounted for. It's the way things are. Sometimes tanks and healers get bored of tanking and healing, and new tanks and healers suffer scrutiny if they're too slow or too new to it that it puts them off wanting to do it ever again, so even more dps queue and less tanks/healers queue.