1st of concidering your gearlvl as it is now, u don`t benefit that much from the mixed gems when u could hit more stm. bosses hit faster but less hard thus more EH counts.
2d aim for 26 food can help .
3d for u got most avoidance talents get revenge for more aggro its ur second highest aggro move, get glyph of heroic strike instead of devastate . and swap last stand for shield wall + talents ( i havn`t tried it but i`m going to since i hear nice feedback from it)
scarzz