been thinking, and came up with two small solutions to reduce quing times (if that's the word)

6 man groups, make mobs with 20% more health, but let 6 people in, which means in a 2 DPS runs you now get 3DPS, which reduce que time by roughly 33% by openning another slot.

(take less adjustment) since I think it's down to the healer if he needs or don't need a support in a run, let healers have two signup options, one with and one without a support, so...again, more DPS slots.
the major issue with this, is that if you see a support guy, you'll assume your healer is bad since he think he needs help, but beside that, I think it's a decent idea

for the record, I'm tanking 100% of the time, and never suffer from que times myself. still had couple of ideas.