VIT will scale with attack power, STR will scale but not as much

[Arrius]

A lot of FF14 progression mechanics and tank busters are tuned around having full HP of the previous max iLVL to survive. FCoB is an excellent example, you couldn't really survive a lot of stuff without being topped off with possibly a Succor beforehand. A3S as well, minus the tank buster part.

It's one of the ways they make gear checks in this game, having enough HP to survive, while simultaneously making higher gear make mistakes less damning.

But it was mainly revolving around that in the said dungeons/raids, with all mechanics being close to that.
I remember in 25-Man that we had to put 3 off healers alone for the tank back then to keep him/her alive, as the damage spikes likely would've killed the tank if left unattended even for a second.

Glad Blizzard did tone that down at 3.3/Fall of the Lich King.