Originally Posted by
Kittyashley
Hmm. We know that Casting Time = Base Casting Time / (1 + (% Spell Haste / 100)). For the spec I gave above, the haste is 12.89%, so for any spell the casting time = base / 1.1289
For the haste spec, the number comes out to 20.82%, so for any spell with that spec the cast time = base / 1.2082.
PoH is a base-cast of 2.5s, so under the first spec the cast time is 2.21s; under the haste build it'll be 2.07s -- a difference of 140ms.
However, since the mastery of the first build is 17.15 and the second build is only 11.87, the first build will continue to tick for an extra 5.28% after the PoH, so targets under the first build might get healed 140ms later but at the end of 6 seconds since the cast they'll have 5.28% more health than the second build.
I'll agree, stacking one or the other is a situational thing, but I still disagree that haste > mastery for all values of haste.