Recovery diminishes at around 2700-2900.
Critical strike rating diminishes at around 2000. Critical strike rating is also diminished by buffs such as the rogue's critical teamwork buff.
Around 2200 armor penetration removes most PvE resistance.
Power however is much more flat in comparison to other stats. Stacking power is the way to go for a pure dps/hps character.
credit and source: Kripparrian NW: Optimizing Stats & Diminishing Returns - YouTube
https://docs.google.com/a/g.uky.edu/...5TW5lblE#gid=0