Thank you SE for...

[Fawkes]

And that's it? BLU cannot survive to a wipe so it's not broken? That's your argument? Please...
It's not because Diamondback doesn't work on some failed mechanics leading to a wipe that it's not broken. You are taking a single exception and try to dismiss my argument with it. Ridiculous.

I pulled hate on Ifrit so I threw up Diamondback and Ifrit just slapped me out of it.

[Fyce]

-Yes you do an LB 2 worth of potency, over the course of a fight, thats still a dps loss, I'm not automatically assuming its just how it works, even assuming you are raised instantly, those 2 mins of weakness will kneecap you severely, yes you mention phase transitions, phase transition mechanics exist on other jobs as well, just not as powerful as this one. Also There is nothing anywhere which is saying they needed these kill yourself abilities to be blue mages, that was a dev choice

To have a DPS loss after a Self-Destruct, you'd need to do around 800 DPS. This is not what any level 50 in ARR was able to do. Very far from it. So it is still a DPS gain. Even more so in AoE situations. And still the biggest on-demand burst damage in the entire game by a ridiculous amount (excluding LB, which aren't on-demand).

-Im assuming you're talking about diamondback here, yeah 1 gcd, with a huge mana cost, and a huge dps loss, where you can't move. Yeah I can see your point, you could use it to cheese some mechanics, But other classes also do things to cheese mechanics all the time, it wouldn't be a BLU exclusive thing.

No job, except for tanks (specifically PLD, because the other ones need a lot of ressources to be spent) is able to basically take a shared raid damage solo by simply pressing one GCD. None. And for good reasons.
This skill, in combination with White Wind, allows the Blue Mage to take almost nothing on raid damage mechanics and heal the raid back up himself. It is a personal DPS loss, but you make the rest of your party ignore the mechanic completly, especially healers, who can keep DPSing.
It is definitly not a tool that fit in the Caster DPS role.

-I would need to be on full health the heal everyone to full, assuming there is a mechanic that requires party healing, everyone has taken damage, at which point the healers will already be healing everyone up, with more effecient/ quicker heals, getting BLU to full for the blu to then heal everyone is just roundabout

You spending one or two GCDs to heal your group to full instead of two 130 potency spells is definitly not a waste. If you combine that with Diamonback, you pretty much have a group wide Benediction on a GCD. Tell me where does that fit in a Caster DPS role?

-These skills don't work on any boss worth a damn, and the percentage likelyhood of hitting means that its often just better to kill trash than wait for it to proc, they are not broken

Who are you to define what's "worth a damn"? These skills are broken on trash mobs, some boss' adds, and even some bosses. You asked me what made Blue Mage unbalanced. You didn't ask me to justify it on cherry picked content (besides, Blue Mage can currently solo T2. Is T2, a proper raid fight in the BcoB "not worth a damn"?). If you can kill Ramuh's adds in two or three GCDs while being level synced, it's broken. Period. And if you can one-shot some bosses that new players might see for the first time, that's even worse. You not caring for the experience of new players or some content is completly irrelevant to the point.
Insta-killing stuff is broken. If you don't think that's the case, then let's just give Doom, Missile and Tail Screw-like effects to every job. Let's see how's that balanced then.

-Mighty Guard is just bad, you still take a fair amount of damage, and again mighty guard and white wind, cool, how much dps are you losing by doing these combo's, how much mana? On a class such as BLU where its personal dps is so low, can it afford to be wasting its mana and gcds away to pull off these roundabout tactics, which are just less efficient than the healer, you know, healing?

It's low DPS jobs that can get away with doing stuff like this the most... because they don't lose much, by definition. And you are ignoring every mechanics where you simply can't DPS. Omega M/F slides? Just pop Mighty Guard, have a healer's shield just to be sure, take 40% less damage than any other DPS, and then heal the party up to full before the bosses are even targetable again in one single GCD.
This is not what a caster DPS should be able to do.

-Transfusion is pretty balanced, if you're in a situation where offing yourself to prolong the healer is necessary, you're probably not meeting the dps check anyway you know?

Depends on the content. Don't cherry pick it.

-Blu's dps is hella low, I've seen it myself 400-500 on a good day, thats abysmal for a level 50 dps. And yes peculiar light is probably too strong, but you know, it wouldn't be the first time square fiddled with vuln percentages.

500 DPS is abysmal for a level 50 DPS? Abysmal?! I don't know what kind of nostalgia glasses you are using, but they aren't as good as you think.
If BLU wasn't limited and had been released during ARR, it'd pretty much be the only job allowed by the community as DPS. 8-man Parties with 4 BLUs would be legion with these numbers, which would mean 40s/60s uptime on Peculiar Light for all BLUs and both healers (if you even need healers at that point).

-On demand -10%, cool. In most fights, reprisal or dismantle or addle can be up for nearly all aoes anyway, having bad breath be on demand does make it strong, but by no means broken, as you lose dps by doing it, and as mentioned, its dps is low to start with, can it really afford to lose more and still meet enrages.

Of course, if BLU only had Bad Breath as a "strong skill" it'd probably be fine. But this is just the cherry ontop of everything else.

I pulled hate on Ifrit so I threw up Diamondback and Ifrit just slapped me out of it.

Congratulations, you managed to find one very vague exception.