It's not necessarily a negative no, and it can be fixed with more/better player coordination. I was thinking in more general situations than focusing on Savage and up though. Savage makes it less of an issue just because players will tend to cooperate and plan more and on top of that damage is dealt in a way that's different from large pulls in dungeons where the healing conflict is more likely (but also less serious).
I can agree with that.I'd just recommend starting from a tank perspective rather than worrying first and foremost about (typal) output. Trim the things that --by taking up X% of the tank's sustain while being, themselves, uninteresting or carrying less agency / skill expression-- make tanking on those jobs that much less fun.
Thereafter, just make sure that their kits both seem worthwhile and competitive in situations both with low and high damage intake.
Once that's done, if tank sustain still seems excessive, don't specifically target any particular type of sustain for reduction (flat or percentile, preemptive or reactive), but just rein things back bit by bit as a whole -- thereby still keeping that kit's parts in balance against each other.
Too much of that sustain coming from percentile tools makes the kit lack apparently relevance when incoming damage is low. Too much coming from flat tools makes it feel less relevant when damage is high. Let the fun of the kit and basic parity/functionality determine the proportions of those tools in the tank's kit, and then just roll the excess back together.
I don't have an exact answer, and again I wasn't focused specifically on Savage. In 8 player content, healer since the tank isn't the only one taking damage, healing from healers doesn't suffer as much. If I'm understanding your numbers, the % is just coming from the total healing in the entire fight, so AoE healing is being reflected in that. It's one area where healers do outperform tanks (and DPS) and it feels relatively good. If we limit the measured healing to that aimed at the tank, the % should change. Likewise since dungeon pulls are purely about healing the tank, that is where overpowered tank healing is more noticeable.I'm wondering what you think is a good ratio there, then.