Define high end?

Savage prog is generally the best time to be a healer, outside of the occasional stinker (The likes of E8S), it's generally a good time regardless of team.

IMHO actual high end teams (Aka those that will spreadsheet out a healing plan) quickly become monotonous once you're on farm unless you're specifically into that and get more enjoyment from chasing logs as opposed to the actual healing itself.

Personally I've not really found Ultimates enjoyable to heal at all once the novelty wore off. Spreadsheeting isn't optional anymore. It's a test of your ability to execute a plan precisely and consistently.

Healing Savage with a more casual group or PF can be more enjoyable if you can tolerate the suffering though. Unlike a hardcore group or Ultimate there's a little room to react, carry and actually feel like you're making a difference.

IMHO where the wheels really fall off XIV's healing is when you've performed at a Savage/Ultimate level and then step back down to casual content. It makes you realise just how sparse, dead and lifeless the role actually is.