High HP really doesn't matter unless you are talking about Yiazmat. It only means that you can't beat them in about 20 seconds with just lucky chains of Quickenings.

Okay sure, Demon Wall #1 did have more than twice the amount of the second one, but what was really hard was beating it before it rammed you into dust.

Demon Wall #2 was only annoying for me because of things such as Telega, Blindga, and Chain Magick, not it's high HP.

Elder Wyrm was hard because of his damn Sporefall attack which inflicted a whole ton of statuses on you.

Really, if it were still ATB, then the HP would definitely be ridiculous. But since you are able to attack almost every two seconds, it's not. After all, when you were only able to do about 100 damage, Firemane and Mimic Queen had about 4000 HP; I don't suppose you think that was also unfair do you?