Blue mage logic is based on a level 75 game

[Prothscar]

The blink effect is inefficient for more reasons than just being completely wiped by AoEs, it's also incredibly expensive. A good BLU won't be using MM, so don't even bring it up. your most reliable ways of keeping alive will be good mitigation sets and a good healer.

I barely even waste time casting Ichi if I'm /NIN, it's an unecessary waste of time in most circumstances. They're useful on a select handful of mobs, but aside from those, you lose more than you gain. Get better mitigation sets and better healers if you disagree.

The loss of 5% subtle blow shouldn't be breaking your bank. Is it a downside? Sure, but it's not horrible. Defender shouldn't be necessary for you to tank, it's much more of a detriment than it is a boon in most cases.

If you need the ACC from Aggressor then idk man.

Not sure why you're against increasing BLU's damage output, it's really not great as it is. Berserk, and, to a lesser extent, Warcry help fix this.