Despite what certain (salty) people feel, BLU has been fairly broken in a weird way since its implementation. It's "OP" now because what job isn't OP in some fashion on relevant content since the ilvl introduction? Take someone no where near ilvl for current content and see how well they do versus someone at ilvl for the content (e.g someone with only 800 accuracy and no gifts/job points versus someone capped off.)
Breath Spells had only 1 use: Killing Tarus in Ballista/Brenner. MP cost for the damage and additional effects doesn't match up. BLU is very balanced in that sense, while you can 'spam strong spells' the more technical spells cost a hefty amount of mp, have long cast times and doesn't scale at all. It's like if you were to use your Cure I-VI and it didn't scale beyond what you'd cure for naked.
		
		




