Originally Posted by
Xandy
Huge DPS loss, never do it. The damage from channeling MG far outweighs the extra shards you'd get from DS.
EDIT: Correction, there are some situations where you want to channel DS >20% but only because of fight mechanics; i.e. in order to maintain channelling during Epicenter on Feng when your tanks suck, etc
Since you're gearing up, I'd say Gem for Intellect when you can and keep your Haste and Mastery relatively even. Once you reach 500 ilvl you can start to Gem pure Haste/Mastery and worry about Haste breakpoints.
Learning how/when to refresh DoTs and when to use Haunt is the bread and butter of Affliction. I can't give much advice on your 'rotation,' but based on what you said, I can tell you that you don't want to keep Haunt up as much as possible; only maintain Haunt when your DoTs are empowered by major buffs or when under a major Haste buff like Bloodlust or Dark Soul.
Oh, and download the addon "affdots" it will make you a better player