What they mean by "change the damage calculations of tanks"?

[Rbstr]

Worrying about HP levels if tanks go full vit is silly.
#1 HP doesn't effect HP/s required, HP over what's required to eat maximum damage is a (small) time delay that can help with reaction time at best.
#2 Strength tanks already carry more HP and massively more passive and active mitigation than DPS classes. Yet, DPS classes aren't punted from groups for DPS tanks. DPS classes still do more DPS than tanks. 50k HP tanks or not, Savage Alex's primary problems are DPS checks and enrages. Adding more tank HP to that doesn't change this balance.
#3 This change would go happen at 3.2 which is a new raid tier. They can clearly design the new encounters with whatever tank HP value the changes lead to. All the old stuff will be significantly out-geared just like it has always been. Yet more HP doesn't change anything about that.

I don't disagree here--my general preferred solution is a split between STR and VIT in some way, with just enough of VIT contributing to damage to make Fending the preferred accessory choice. This will allow the developers to better predict both tank DPS and tank health pools when designing future content, which should (hopefully) result in better encounter design.

If vit is better than strength for damage there's no reason to ever carry strength. That basically means it's irrelevant if it's a hybrid between vit and str or vit alone.
If you want strength to mean something still it has to be better than vit for damage. You need a different control, like tank busters that require several vit accessories to survive or some kind of strength cap, in order to push vit accessories then.

[Alahra]

If you want strength to mean something still it has to be better than vit for damage.

STR should "mean" about as much to tanks as VIT means to DPS, honestly, though, if they want tanks to fit into the same gearing paradigm as every other class. That is, my feeling is that they will leave some fraction of tank damage tied to STR so that the STR in place on left side gear still has a purpose, but not so great a purpose that tanks are encouraged to meld STR or to use Slaying accessories.

While a STR/VIT split won't, in practice, end up any different mathematically than a pure VIT ratio, it fits better into the existing gear/class paradigms, as each class has two primary stats that matter to them. The non-main one of them isn't supposed to matter so much that it complicates accessory choice, though.

There are other ways to make STR have some effect for tanks, of course. They could revert the HW-changes to STR's effect on Parry and Block, for instance (and probably scale them up some), and then make VIT their full attack power stat. In some ways that would make them mirror the other classes a bit better: primary stat for offense, with a secondary stat that contributes to survivability in some way. But they only mentioned changing damage calculations when they discussed how they were going to address the issue, so that's where I assume they'll be doing everything until we get more information.