I don't necessarily agree that HOT spells (ie GCDs) are inefficient, wasteful, etc. I think that their 'usefulness' is simply a victim of 'how much gear do I have'. In something where you have low gear, or the item level is locked to make it 'always hard', (aka, week 1 Savage or Ultimate), HOT GCDs are pretty good in terms of 'efficiency'. It's when we outgear the fight by 20 ILVL because we have BIS, and people take less damage because they're also in BIS (higher Def/MDef stats) that we feel we don't need those spells anymore, because our OGCD kit can handle the healing required.

For example, I don't want to imagine trying to do something like Natural Alignment from P8S, in Week 1 gear, without using Medica 2 or Regen to keep HP levels more stable. Maybe AST could get away with it even in Week 1 because it had so many OGCD options (with a lot of them on a 60s CD), but I tried AST there in prog like a single time, got hand cramps from trying the opener on loop, and thought 'it's not worth the effort or the discomfort'