Don't forget, premade also means stacking the odds in your favor with proper class composition and geared players. This is a HUGE advantage.
I run premades, I solo queue, I do both. I would much rather have split queues.
Premade doesn't = Gear players. Likewise PuG doesn't = Recruit Gear. Gear and Gear gap is a seperate issue from premade vs. PuG. As for class composition, that is an acceptable/valid argument. Having a premade on your team does increase the chance of having atleast 1 healer and 1 tank.
Would you rather split queue's, or a flexible matchmaking system that matched premades to premades, PuG's to PuG's, or an equal mix of Premade+PuGs, with gradualy lessening balance per minute to keep queue times for both sides to a reasonable time? Not to mention this system would also cover the problem created by a split queue, which is incomplete group filling and backfilling.