Gargoyle adding health makes building health required. That's the point.
that's not true at all.
Gargoyle giving 100% more hp for 4sec is EXACTLY the same sboost to survivabillity as 50% damage reduction.
For example, a 2k hp target getting hit by 1k damage vs 4khp target getting hit by 1k damage.
Normaly, the 2k hp ends with 1khp so 50%, the 4khp ends with 3k so 75% remaining.
With current stoneplate, the 2k becomes a 4k for the duration, so you drop to 75%, and since the %stays after the effect, you end with 75% of 2k = 1.5k hp
A 4k becomes 8k, dropping to 7k, so loosing 12.5%, whoch means after the effect ends, he's on 87.5% of 4k = 3500 hp.
In both cases, you end up takeing half as much effective damage as without the active, which equals a 50% damage reduction.
So in the end, no matter how much hp you head, the effective damge you've taken once the effect ends is 500, which is 50% of the damage you took duering the effeckt.
The only real difference is the interaction with other effects. The current bonus HP benefits %scaleings, but also is vulnerable to %damage while also beeing a good target for lifesteal(especially %hp based lik BotrK) However, it doesn't benefit flat heals and shields in any way.
Damage reuction would meddle with scaleings off the user, which would mean flat healing/shielding would benefite as much as %based heal/shields. It also would cut the lifesteal against the user in half since less damage done = less lifesteal.
So it's in no way 'super abusable', squishys and tanks both get exactly the same effect durabillity boost than the do with the current hp boost, the only potential abuse case would be strong flat shields or heals, so mostly supports keeping a stoneplate target alive.
And no, lifesteal on a stoneplate user is no issue at all, because there is still the 60% damage reduction, which means you lifesteal is also reduced by 60%.
I also don't see how the hp-boost is any more visible, power you hardly ever have you eyes on the exact hp value off the tank duering a fight, and other than that number change, it has absolutely no visible effeckt that %reduction wouldn't have.