CORs (Quick Draw) and SMNs can consistently deal over 1k dmg to Yumcax, without Elemental Seal my BLM couldn't go over 100 dmg, with Elemental Seal I couldn't go over 550 dmg...

DDs these days have no problems dealing damage... BLM can only deal good dmg to select mobs in this level range of content, and the fact that we easily steal hate and have to rest MP if we want to keep up with DDs means that BLMs are useless in this content. You can't get good evaluations in reives with BLM, you have to pretend you're a WHM and just heal people... Go ahead, give it a shot... You'll quickly find that trying to use offensive magic is risky if you can actually deal decent damage and it's always a waste of MP.