Although this is bugged and he abuses it, i tested this after i saw this report, and although it's not as big of an increase i expected (expected multiple thousands), this "only" increases your spell power by 300 instead of 28, so although it depends on preference i don't think it's worth losing 170 haste/mastery for 300 spell power as an Affliction Warlock.
This guy however does abuse the bugged enchant.