Damage reduction meta still not predictable. Until I have played the boss fights myself first hand I won't state anything like a fact, however, assuming that the next tiers damage taken from a tank PoV follow the same pattern as this tier, it won't really be that useful.
It will be a nice to have but nothing game breaking. Nothing prevents that meta from being down when I need it and up when I do not need it.
From a tanking PoV, there are 2 things you want.
Static effective health - Stamina, armor, magic damage meta, etc, basically, anything that ALWAYS help you, always is there for you, stuff that are never gonna give you up, never gonna let you down, never gonna run around and desert you
On-demand damage reduction/Effective health - Mastery, CDs, good on use trinkets (read as, not dodge or parry), etc
That meta is just plain TDR, and that is not really that great as a tank, nice to have but not that we die for it. That damage meta looks nice for 10 man PoV, to bad it is just not the effect, I would love to have the stamina + the effect from the damage meta.