So I've spent these past couple of weeks learning how to tank A8 as PLD. When I first started, I was using the ilvl 200 Eso weapon, no upgrades because I'm lazy. But I've managed to hold aggro from DPS with ilvl 240 weapons in Sohr Khai and Hullbreaker Isle HM before. Now I have the upgraded lore weapon for PLD, so it's easier.
Of course I'm not the best tank, PLD is hardly my main. But having played all 3 healer jobs to 60, I do believe I have a fairly decent grasp of how aggro works, as well as how regen buffs generate aggro. So that being said, if a WHM decides to pop Medica II/Asylum, and especially if an AST decides to throw up Collective Unconscious, while Brute Justice is spawning, they will get aggro, and there will be nothing I can do about it.
I can Provoke and Shield Lob all I want, I will not get aggro. Especially if the healer in question then decides to run around like a headless chicken, therefore leading the boss on a little jog, so I can't use my close-range aggro skills. Especially especially if I happen to be paralysed, and half my actions are being interrupted.
Have I, as a tank, screwed up horribly and led to deaths and wipes before? Yes, of course I have. Incorrectly identifying Blaster's AoE is fairly hazardous, and I've killed people with that mistake. But I will make active steps to rectify that mistake and improve.
Even so, there are some things I simply cannot do, and keeping aggro off a healer who keeps spamming regens when a new boss is just spawning, giving me no time to even attempt to build aggro, is one of them. Being told "never had that problem while i was tanking" doesn't help. Nor does calling my playing "shitty tanking", nor does being told never to queue as PLD ever again, by condescending little brats.
I know it's popular to blame the tank these days and treat healers as precious little angels who can do no wrong even when they actively make things more difficult for an already-struggling tank, for the sake of their convenience, but once again, as someone who has played all 3 healer jobs to 60, healers need to get their heads out of their asses.