I've recently replaced my black mage (Terra) with Celes as a second spellblade user. It's working pretty well. I will switch Celes out once she hits 50 not sure what I'll replace em with. Vanille is tempting since they look like they're competing well with Terra for the black mage slot, since I'm using Balamb Guard Armor (light) for Terra anyways. Having 4 melee attackers (Cloud, Wakka, Kain, Celes) makes things go quite quick. For farming hard dailies I usually just give Tyro one of my other 5 star weapons and I can auto battle through them fairly easily.