Im IL 540 with 16,875 Haste Rating (39.71%) and that is with matching my gem slot ONLY if the socket bonus gave me strength or crit. For yellow I used 320 haste obviously, for blue I used 160haste/160hit and for red I used 80str/160haste. Whenever I didn't need the socket bonus I go fully 320 haste. Haste will ALWAYS be the best stat because every 1 haste = .6 dps compared to 1 str = 1 dps. 320 haste = 192 dps and 160 str = 160 dps. IF THIS INFO IS WRONG PLEASE LET ME KNOW =]
Also as prot I hit around 40% haste with 17.2k Haste Rating.
I wouldn't recommend going full haste gems with all of your RET sockets however I will try it on sims.