Since I just came back to playing WOW I can't comment on LFD as a boxer but in WOTLK I played the healer and 3 DPS and grouped with a random tank. I found a few that were compentent so we did this all the way to level 80.

Later in the game (once I could outgear the instance) I ran my own 5 mans - tanking with my paladin and healing/dps with the shamans. It was doable but kind of a pain in the ass to.

I thought 4x (healer and 3x DPS) was way easier.