The MP is not what concerns me, but rather the lack of MND. If it was 1INT for 1MND, I'd trade it in a heartbeat for spells primarily modified by INT, but 1 for 4 from Prism Cape is a lot less clear. For Blue Magic spells modified by both INT and MND, this may not be a showstopper.
Dubya, the reason why true BLM or SCH or w/e would chose 1INT over 30MP would be resist. If your nuke is resisted then it would cost alot more MP to recast it, not to mention waiting on it's timer which could save your life. This is the same argument as Mahatma > Jets.
Umm >.< If your that butthurt over MP 20, you can always macro this in when you cast, and idle in something like Blue or Invigorating cape... but that wastes precious macro space, for 20MP which, WILL be gone after 1 cast of anything.
> If you're a high-level BLM or SCH, you should know by then that INT is more valuable than MP... <
1 int for 30 MP seems like a very bad trade. Blizzard-1 is 30 MP, If you think you can't do the extra 2ish damage you will get from 1 int with Blizzard-1 then go for it