On literally every job except MNK I prefer the tank to pull as large a group as the healer can sustain (they don't have to heal for long, usually).

On small pulls, a healer can more or less fall asleep, the tank is never in any real danger. Both the tank and healer are underperforming in relation to their potential.

On DD jobs, on any pull of more than 4 mobs, it is faster to AOE them down (I think the number is something like 5 for MNKs, correct me if I'm wrong).

Obviously this is only something you can do if everyone's i-level is up to it (about 10 over minimum required ilevel for access) and you don't have 2 MNKs in party. BRD, DRG, NIN, BLM, SMN (to an extent), WHM, WAR all perform better on mulyiple targets.

I find it both faster and more fun.