Feedback TLDR; It feels like needed QoL and buffs to non granite and nerfing Granite; making players choose more heavily between playing it with or without investment into granite.
This may seem like minor numbers things, but the proposed changes are effectively loosing a defense toggle (~3%) and a resist all toggle (~6%) OR pay a slotting tax that i feel it could avoid; as you will have to slot more to get the same effect you are basically making stone armor take an extra power/spend slots for the same survivability as before if going/using granite. The difference between running granite and not running granite becomes even more extreme as you not only drop huge self nerf (-30% dmg, -65% recharge, self slow;though you can slot for speed and "avoid" the slow) you would now also gain extra offensive capability in the fire dmg rider effect to your attacks, 20% recovery, +15% recharge (net difference then being -80% effectively for granite!?), bonus perception, psi coverage etc. The extra functionality does feel needed, however, and gives a greater capability to be granitless - for stalkers and scrappers a given as they lack the power and maybe dps brutes but tankers will loose out on this as it is when they need to go into actual tanking when making their builds for power/enhancement slots.
The slotting required to counter the move of def/resist to a passive takes the slotting of basically another whole power, and also requires you to take the power in the first place (as it could often otherwise be skipped or was simply muled for psi resist/minor things). Taking and slotting an extra power (at minimum 2 slots for defense and 2 for resists) beyond its prior mule status at best is a hefty tax for access to stats you would have already gotten prior, for the tanker above level 26 you would often only get some reduced endurance cost from this rework AND have to toss another power's worth of slotting to fill out stone skin properly. IF that's to be the tax for granite, perhaps some of the other downsides could be considered.
Some may view this as not mattering all that much, as a near self capping tank has less use for buffs and high level play is rife with them, but with coming challenge modes and other things, or just for when you run teams that aren't buff heavy, it can matter and i'd like to think of the set design towards those also scenarios.
If one proliferates buffs to stone skin into the other armors instead it would be a better service to the set than merely moving them from granite to stone skin; include other features to stone skin instead if making the power more useful/dynamic - such as putting the brimstone fire effect into the passive armor or making granite a toggle that adds in addition to the other toggles instead of replaces. If you put the brimstone rider effect on stone armor it would give granite some minor buff as well as the general play useage while keeping stone skin as a valuable power everybody would want to take.
Point being just moving some def/resist from granite to stoneskin is a net nerf to total investment required for survivability for tankers (with huge -recharge they already felt like they had less buttons than other tanks, making them effectively loose slots takes away more) please be careful you don't tax an already taxing set/ability (granite), its already feeling rough to play and now its getting even worse comparatively, give it some love too! Just a nerf of -3% defense/-6% resists (net effective with similar investment) feels minor but harsh in conjunction to the other buffs its now also missing out on (and if you're now running granite-less you need to more heavily slot the other powers), potentially such as decreasing the detriment to using it if the difference is already going to be increased otherwise.