Resolve Tree
I feel like the new Runes system buffed the damage people can do by a huge amount, but this tree doesn't do a good job of making tanks tanky. It does an excellent job of making tanks do more damage, but that it really a bruiser thing, and not a super tanky thing.
For the keystones, Grasp gives slightly more healing than it used to, and does slightly more damage, and now gives 5 max hp each time. Not bad, especially if you can proc it a lot early on, although there aren't too many people who will let you hit them for free every four seconds, usually because you will kill them if they do.
Aftershock is usefull on tanks with CC engage, but, just like courage of the colossus, it goes on a decent cooldown, and doesn't last for a huge time(this could be a problem). Although it is useful in teamfights, if you are laning is not really useful, because if you hit someone with a stun, they wont be hitting you for the next second, making half the resist buff less useful. Maybe if it can be activated with large and epic monster (with a moderate cd) can be more useful with tank junglers because this is not definetely a laner rune.
And Guardian is basically only viable on junglers and supports, and can be annoying to proc, to the point where I have literally only seen it on Braum (W) or Tahm Kench because he already wants to stand by his ADC to eat them if anything goes wrong.
For the first tier, Here is where the problems of tankiness turns more evident, Although tenacity and slow resist are useful, and may let you escape or CC the enemy more, Unflinching is not an increase in tankiness as such. It need a quick access. Maybe with something like this would be better.
PASSIVE: You gain 8% Tenacity,. PASSIVE: for each of your summoner spells on cooldown you gain 8% additional of tenacity, stacking up to 24%.
Demolish, while good for splitpushing and gold generation as a tank, doesn't make you any tankier.
Font of life is the same as the old stoneborn pact, but without the 5% max hp, so doesn't make you tankier. Maybe this can be one that need some attention.
PASSIVE: Impairing the movement of an enemy champion marks them for 4 seconds. Allied champions who attack marked enemies heal for 5 (+ 1% of your maximum health) ** and heals you half of that amount.**
Second Tier:
I really don't like either Iron skin or mirror shell, the 5 and sometimes 5% buff is going to rarely be game changing in the first 10 minutes,** this both really needs a rework to be more useful and no so ocasional**, also the 8 and always 5% buff for both is better after 10 minutes. Conditioning does do a decent job of increasing tankiness, assuming you already have armor. (although 5% isn't huge, because when it's numerical value is larger, the reduction you get per armor is smaller)
Third Tier:
While Overgrowth makes you tankier, you have to be near 400 CS to get the 5% max health that was on bond of stone, and then you start getting buffes from the old masteries. If, like me, you took % hp runes before, then you have a lot more CS to go to make up that deficit. Maybe a increase to 0.3% instead 0.2% would be better in tankiness.
Revitalize is useful on people with constant heals, so can make mundo and maokai a little better, but if you don't have heals, it is not useful at all.
Second wind's heal is very small, amounting to 0.4% of your missing health every second. While this may reach noticible levels on low HP, it will only restore significant health on people like straight tank chogath or sion, or possibly mundo, just because of the sheer health they get, or people who are about to die anyways. It's 6 flat so I need to be honest: This seems pretty bad. Maybe needs a completely redesign.
In conclusion, everyone does more damage, including tanks, but tanks didn't actually get much tankier,
