[Geckothan]

Terrible idea, Affliction gains very little from crit compared to what it gains from spell damage. Just keep stacking spell damage. I'm sure this idea has been discussed to death and yet people (people with commonsense anyway) still stack pure spell damage as Affliction, and you should too. Gemming crit as Destruction is also pretty poor, you should be stacking spell damage and spell haste in that case. You're right that spreadsheets and simulators make the assumption that you're standing still casting constantly, but I'd much rather trust those numbers than go by "feel".