Thing is that weakness isn't a bad thing, various tanks having to adjust to different mechanics in various ways is a good thing in my eyes, and it's not like we don't have tools to make things easier. Smart timing means we can cover the three major threats (autos after Gravity, tank lasers and Spear of Paradise) with just two cooldowns, and there's a swap right after. If that isn't good enough, we can use Hallowed to completely ignore Gravity if we want - that's what I started doing in early weeks when healers struggled to keep me alive. I feel like a lot of arguments in this thread are founded on the idea that Sheltron being weaker is a huge issue, but I feel like it's one of the things keeping PLD particularly interesting for me. When we have less mitigation tools we have to find unique ways to use what we have, and there's certainly no situation in the current tier that can't be mitigated properly with good play.
We have two particularly strong niche uses for our gauge, in both the best OT skill in the game (Intervention is absolutely absurd in moments where both tanks are taking damage) and one of the most abusable skills in the game (Cover is perhaps a little too weak now but I've saved my share of runs with it in scenarios where nothing else could). Divine Veil is... admittedly a little finnicky, I don't like the activation requirements much, but it's an incredible source of raid mitigation if you plan around it. Also, if I'm thinking correctly, it works out stronger than Shake if Off on a lot of classes. As for Passage, that has a long cooldown because it's absolutely ridiculous when you realise you can just flash it on and off as an oGCD; turns out requiring the party to stack isn't a huge problem in Savage when everybody stacks anyway. So yeah, I'd say having the most variable toolkit which can cover nearly any situation if you play well is worth the loss of a minor defensive tool when we already have the best invuln skill in the game.
Could be, I've never actually been able to find the specific number since everywhere I've asked has said either 75% or 80%. 75% sounded nicer so I went with that, but it could be wrong.