Originally Posted by
ThePants999
You only get "hard and fast rules" relating to specific stat numbers when you have
- softcaps, where you reach a limit above which a stat ceases to offer value in one particular respect. For example, Holy paladins have a point above which Holy Shock has a 100% crit chance during wings, which makes crit above that point significantly less valuable.
- breakpoints, where a particular stat value offers a specific benefit to reaching, so the stat is massively valuable if you're just below that value. Most haste-related breakpoints vanished with the haste rework Blizz did. Now, you only see haste breakpoints related to fixed-duration buffs/debuffs. Ret has two (well, one for most of us):
1. how many GCDs fit into a Judgment window
2. how many GCDs fit into the legendary cloak buff window.
I can't remember the exact numbers, but if I remember correctly, the Judgment-related breakpoints are at something very low like 12.5%, and something very high like 35%, which means it's pretty much irrelevant to most of us as you're practically guaranteed to be over the first breakpoint and clearly won't reach the second. The cloak-related ones are at ~12% and 50%, so again, pretty irrelevant.
That said, those numbers are for perfect play with every ability used precisely on the GCD. Haste beyond the theoretical breakpoint gives you breathing room for when lag or mistakes introduce sub-optimal timing.
Everything else you see - 20%, 25%, whatever - that's all garbage that people have pulled out of their arses with phrases like "it's much more comfortable above 20%", like they could tell the difference between 19% and 20%.