Man don't drop BLM. I love playing BLM. And there's nothing that feels quite so good as those 10K+ crits.

Though I do understand the worry of losing a ton of DPS because you're unfamiliar with a boss' attacks, transitions, and other mechanics. So personally, I play DRG as a "Learning Class"; finding it the easiest to adapt on the fly and learn a fight with. Plenty of mobility, and the DPS loss is more forgiving if you wind up dropping a combo or BotD when compared to MNK or NIN.