It's actually a huge plus to do as big a possible with any melee. MNK's AoE is competitive during Perfect Balance (only once every 3 minutes), and beyond that it's pretty bad (but still worth doing). DRG's also competitive while fully buffed and with Dragonfire Dive, but it's very TP draining and a little less strong while waiting for DFD to recharge.

Also, doing multiple pulls is really draining on TP. If a melee can spend all they have on one pull and then recover while going to a boss, it's quite a bit better than going pull by pull and having to do less AoE, or going dry.

Speed runs vary based on who you're running with but the general rule of thumb is, ideally, it's better to group up than do multiple small groups.