Can't hurt to try, I can say that Tiamat was ALL OVER the damn place today and didn't flail.
Maybe try the following:
Tiamat lands, 2 hrs, PLD/NIN cover until Mighty Strikes is over.
PLD/NIN swing around behind and crawl up Tiamat's rear. First TP person SATA unload onto PLD/NIN from the rear. Presumably Tiamat turns, closing SC person SATA unload onto PLD/WAR. We could greatly increase the dmg, I dunno if that will cause a flail, but we can certainly try it. If it works that'd be substantially increased damage over time.