1. dont gem for poor socket bonus (4/6 str)
2. Mostly gem for 20 arp (if you want to please most raidleaders) or 20 str (until you got some icc gear)
3. you can change pyrite infuser with banner
4. as long as your dps is not from icc, dps is good for the gear
Updated my gear and changed enchants. I first went with Str gem as everyone suggested, but my dps actually went down a little bit. Then I downloaded Landsouls spreadsheet and played with items/enchants/gems.
Long story short; I gemmed for expertise a lot. Chucked some str items in exchange for agi. Went armor pen all the way. Sitting at 765 armor pen. Not too shabby now. Upped my DPS by 1k.