I only play WHM on Tiamat and I filter only for the tank party, but there are tons of times when I see people's HP dropping at Tiamat. It's not every AOE move, but I've seen it happen even with good tanks at the right spots. BLMs also cap hate and get drawn in (or Tiamat herself moves, especially after roars). I think that it'd be far wiser for the COR is ready to support the BLM party is necessary than to insist on using only DD gear.
And again, that's not to say the COR shouldn't be using QD... just use MP gear and switch gradually into DD gear as the MP pool dwindles. I doubt it results in enough of a loss of "Cor dmg" to justify even one potential BLM weakness.
Not really, when I played, I was the COR for one of the tank parties during AV attempts, and I had about 200-300 MP I think. Only time I got really strapped for MP was when things went occasionally batshit and I ran out. Evokers/Ballad/Refresh is more than enough to keep a COR/WHM MP pool up.Perhaps AV is one example where MP gear would be more helpful than it normally is - but fuck, nobody is beating it, so until he's being beaten and the strategy shows 550 MP being enough and 300 not, I fail to see much signifigance in it..
So, your right, you don't need nearly that much MP, hell, for the average event, I was more just burning MP to keep pendant active than I was for actually curing purposes.
Edit: There's more pages to read, durrrrrrrrr.