Haste is the most complex of the healing stats, and often appears to be the least well understood. Its effect is a combination of added throughput, increased mana consumption, and increased HoT healing due to those “haste breakpoints” that are so easy to look up online but so hard to evaluate in importance. Part 2 in this series, linked above, gave some high-level comments on the behavior of haste, and generally concluded that based on its basic function, it’s likely to be unattractive. I said that I would dig into its effects on a class-by-class basis in the future, and that is what I’m doing in this post.
Incidentally, this post is written from a patch 5.4 perspective. Among various other things, haste will have no effect on the RPPM proc rate of the legendary meta (and legendary cloak), greatly simplifying the analysis.
First, a slightly different framework for how haste effects the two main categories of spells. We’ll refer to this throughout the post.
1) Non-HoTs. Haste does not increase the healing per cast (HPC), nor therefore, the healing per mana (HPM). It increases the healing per cast time (HPCT) by 1% every 425 rating. It is worth pointing out for comparison that a typical mastery, like Druid, Holy Priest, or Paladin, increases all of these metrics (HPC, HPM and HPCT) by 1% per 480 rating. In general even from a pure HPCT (spam throughput) perspective, haste tends to be only slightly ahead of stats that increase your healing on a per-cast basis.
2) HoTs. Haste now increases the HPC. An important point I want to press on: in the long run, haste still increases the HPC by 1% per 425 rating. The “haste breakpoint” (HBP) phenomenon means that that increase to HPC comes in clumps, but the average gain is unchanged. Especially late in the expansion when the difference between a high-haste and low-haste build may be 20000 rating, it’s this overall scaling pattern that generally determines the relative attractiveness of the two. HBPs tell you what haste points to “snap” to in your reforging, but generally don’t control the overall value of haste. The only general exception is the first non-automatic HBP for any important spell, which requires a smaller investment to reach.