The sustain of the other roles massively devalues the healer
Put it this way, with the sustain the tanks and DPS have instead of needing to heal every 30 seconds I only need to heal every 90 seconds, so every piece of sustain that’s given to the other roles is one less piece of healing I actually need to do and more broil I’m stuck pressing
I should also inform you zero healer clears of all casual content is relatively easy in a decent group and no healer clears of savage isn’t uncommon