Regarding the achievement You're Really Doing It Wrong I made several (about 20) tries on this. According to Wowhead's comments, it should be a cakewalk... I once got to wave 10 but did not make it there because I did not have a Berserker buff left. In most cases, I struggle even earlier, mostly at wave 7.
My gear is my normal tanking gear (Armory) including those with Bonus Armor and with Tectus' Beating Heart and Tablet of Turnbuckle Teamwork equipped. My gear is optimized for Multistrike, although I know that sockets and set bonuses are not applied to Proving Grounds. I use a flask and buff food.
Is there any advice on how to pull more DPS? Talents? Glyphs? Specific items that I should farm?