30 STR always.
3 Slaying / 2 Fending or 3 Fending / 2 Slaying, depending on what you're more comfortable with.
13500-14000+ is good for A1S, could probably even get away with less.
The only times you'd want to be in Grit is when you're getting hit by the tank buster, and that largely depends on what mitigation you're using.
http://imgur.com/Csnxu1p
Play safe at first, don't try to do anything fancy. As you get used to the fight, start taking risks and figure out what your (and your healer's) limit is.
I don't play DRK so can't give any DRK specific tips, but I'm sure there's people more qualified who can.