A magic resistant mob covers all those bases. Everyone TPs so ridiculously fast with haste (spell) and march/geo-haste that the type of melee you bring really doesn't matter.

People don't particularly care whether to nukers are GEO, SCH, RDM, or BLM so long as one sc results in the mob dying.

Give me a mob designed for SC damage, and I'll bring a monk, drg, samurai, I don't care. I already do, just for only one spot in the party.

Another reason Apex Colibri would be perfect: Feather Tickle stops putting an acc check on the tank, and lets them be more concerned about tanking (which is hard on newbies, being tankable enough, and meeting acc checks).