Stoneskin is definitely worth being casted whenever there's an opportunity in fights, but as a regular rotation? I'm not so sure. In theory stoneskin will mitigate the same amount on both tanks. While it does provide a bigger shield on WARs, thanks to our +25%hp, it will be destroyed quicker than a PLD, who has a -20% dmg reduction baked into his tank stance. There should be no difference, in terms of how much dmg stoneskin prevents, on either tank.
Mathematically there's zero difference between the two, but in practice in combination between SS and Warrior abilities, the impact on overall incoming damage was dramatic.
And to be clear, I'm not talking about spamming it, nor using as a replacement for regular healing - simply having it as part of the combat rotation where when the Wars hp approaches cap, stoneskin is thrown on,
rather than sitting idle or wasting an overheal and it's thrown on at the end of every fight so that it's ready at the start of the next fight.
Trust me, if it it was as simple as 'this WHM is bad/undergeared' I'd notice (I've done runs with WHMs who were slow to cast anything, didn't use regen, didn't use ss, so my health was like a pingpong ball).
But I've done many runs and the consistently smoothest runs healing wise have been SCHs (built in shields + mini heals streaming in from pet), and WHMs using ss and regen.
The thing is, ss lets WHMs 'overheal' without actually overhealing or wasting healing. And if they happen to fire it while Thrill of Battle is up, the effect is even larger.
The side effect of that 'useful overhealing' is dampening the impact of the next incoming round of damage, and with any luck at all with dodges or parries and cooldowns, it lasts longer. Even if it doesn't, it cuts the hits enough that you can promptly use Inner Beast to bounce back up to full or near full.
If the WHM is only casting cure and cure 2 freecasts/hardcasts, not using regen frequently, and not using stoneskin, they can't 'cap' your health, and you never get an easy opportunity to use Inner Beast without wasting the healing.
Heck even Bloodbath is noticeably more useful when it's triggered with stoneskin and regen running when used in conjunction with (always) Berserk and (often) Inner Release (even rarely Unchained, but that's actually long enough of a cooldown that its not up every pull).
Note we're talking a game of inches here - assuming optimal use of stoneskin, regen, beast, bloodbath, and thrill, you're saving say what looks like along the lines of just a few healer GCDs - not that impressive.
But in practice, I've consistently had smoother runs with WHMs that did use it frequently over those that didn't. Mana efficiency just isn't a big deal when you're clearing trash (in a group with good dps, I'll have to stop for TP regen before the WHM needs me to stop for mana regen).
If you're freeing a few gcds for the healer to dps or even idle, damage output is higher, healing threat is lower, and the run is smoother.
Boss fights and serious HM primal battles are something else, it's still useful and important, but on something like HM Titan, I'm simply assuming my WHMs are good enough to be capping and layering ss on when there's an incoming mountain breaker or whatever. If they aren't, you're likely dead anyway even with 7k hp
Look at it this way, say your tank has just 6k hp as a War or 5k hp as a Paladin. Wouldn't you rather your tank has 7k or 6k? When they start fights with ss on, they do, and when ss is used midfight to cap them, they do (when it's used on that 6k war who used Thrill, now they're sitting at 8.5k - that's a lot of health to chew through before they need another heal - on a 7k War they're a hair off 10k).
Stoneskin is slower to cast and less mana efficient than usual cure I/cure II usage, but it is not less efficient when it is used at or near full hp when another cure would be wasted overhealing and threat.
Admittedly, I'm probably writing a lot of words that are already well known to WHMs who read here, and the bad ones who don't use it online aren't going to be changing their habits anyway
