I actually got this the other day, but I am now a Champion of the Frozen Wastes!
Interestingly enough, the last heroic I needed to do to complete this achievement was also the first WotLK heroic that I ended up tanking instead of dpsing. It was heroic Oculus.
Big achievement for me, because I've never been a raider in any sense of the word, and even in BC I didnt do all of the heroics. But now I've experienced a full clear of Naxx, EoE and Sarth as well as all heroics, so I'm kinda happy with my Paladin right now.