As a raid geared warrior, i tend to do like Lianeb. The first criteria on upgrading an aug is if it has a higher AC, then if it has HAgi, HDex or HSta, with me favoring Hagi > HDex > HSta. So i'm balanced on HAgi / HDex and don't go full one or full other. If group mobs negate all Hagi / HDex of group geared tanks, then we can assume that raid mobs do nearly the same on raid geared tank, which means that having HDex doing 2 checks instead of HAgi doing 1 check doesn't matter much. And HAgi AC boost will remain here. Someone did some parses recently too on some group named mob with various HDex / HAgi levels and the result was that at some high HDex / HAgi numbers that raid geared tanks have the gains were limited. Putting them HSta not to shame then, hence why i would not be mad to upgrade maybe a Hdex aug with a Hsta aug if this last one has more AC.And Sta means HP which helps on big raid AOE atm. I still believe that HDex /HAgi are still the way to go if you have some low numbers in it, but once you reach some "end game numbers" in them it may not be as much powerful than it could before (i don't say it's useless as Heroic aren't capped).
