None of the mechanics that you've described actually made taking harder.

Snap enmity was historically the main aggro related challenge. For this to have meaning, you need an add spawn that's capable of oneshotting a healer if not grabbed instantly, like a Shadow of Meracydia or Gordian Sniper. Maintaining an established enmity lead was never challenging. Nowadays, though, players are probably just as likely to just weave in an oGCD burst heal to grab aggro rather than fuss over spawn locations.

TP management wasn't interesting for tanks. It involved either bringing a BRD or pressing a button at a predetermined TP value. I'm glad that it was replaced by more interesting resource management systems. Likewise, lengthening the recast on Sprint and making it useable on melee jobs actually raised the skill cap around the ability, if anything.

I know that there's an ennui around tanking and healing at the moment, but it's not for the reasons that you've listed. If you want to make tanking challenging, then you have to work on making the positioning and survival elements more difficult.