I'd rather they kept 8v8 as-is. If they want to add a 'balanced' option they can have a separate queue (which I won't use) but it's very rare that people won't switch, and even though I strongly prefer playing healer I would hate not to have the option of switching! Being able to change roles to balance a team is something I really enjoy, since I don't have to make sure I strategically queue to limit the chance of being a double WHM combo or something else I dislike. I've won plenty of matches in 8v8 as solo healer or with no tank. Once I was the sole DPS (having changed from healer at the start) and we still won. Somehow.

You can spot most bad players really easily if you play a few matches. That and people without enough HP to be worth healing. But I'd rather they fix the other 100+ things wrong with PVP right now before adding balancing to an inherently unbalanced training mode.