Originally Posted by
Larynx
Versatility says sup.
Intuitively. 10% haste is a 10% healing increase to any periodic effect, in addition to reducing the GCD/Cast time, so haste double dips into these. It's still not enough healing to make haste outweigh the throughput and HPM benefits of crit though. Haste is only ever more HPS than crit if you're global locked for a fight, and, well, a lot of fights you're not going to be global locked or you'll be forced to conserve mana through more efficient spell selection. Crit is ideal here. When we get more crit and don't care about mana as much, haste will be much better.
for the claim about haste and being global locked, in a 10 second period you can cast 2 riptides and 3 HWs with 1 second of dead time. Unless you can fill that dead time and cast another HW, haste is having zero HPS benefit for your total healing done outside whatever benefit you're getting from the HoT portion of Riptide. Haste only increases HPS if you don't have enough time to cast all the spells your mana allows for.
These two passives do not scale with haste in any way.
Cast time is determined by the formula: Base/(1+Haste). QA and TW are independent of this, and simply change the base cast time. It's simply Base(1-Mod) = New Base used for the haste formula.
eg. 25% haste and a 30% mod being used for HW.
2.5(1-0.3) = 1.75
1.75/(1+0.25) = 1.4 cast time. 25% reduction.
Or,
2.5/(1+0.25) = 2.0 cast time. Also a 25% reduction.
QA actually devalues crit in some ways, not haste. If QA reduces the cast time of a spell below your GCD, then the effective cast time is still your GCD. This happens specifically for Healing Surge, since it's a 1.5s base cast time. I was actually incorrect when I said that haste doesn't scale with QA/TW. It actually does, and it's only positive, but only for this very very minor situation. HS with 15% QA is 1.28s cast time, which is around 17% haste, after which QA no longer benefits from haste.
edit: The same applies for HW actually, if QA and TW stack. Depending on how they interact, that's either 1.15s or 1.29s cast time. A 1.15s base cast time spell would require 30% haste before the GCD matched the cast time and you'd get the full value out of QA+TW.