Hi first post so sorry if im doing something wrong

Anyway, im a level 75 warrior and im just getting into tanking as my main spec is arms. I've got pretty decent tanking gear i think, other than my weapon which is a bit of a problem. The main thing im wondering is what would be the best tanking weapon for my level and what stats should i be looking for?

Im also not sure of my rotation and if im doing the right kind of things, usually i will charge -> Devestate a bit -> Shockwave -> Thundercalp -> Devestate and revenge when it is not on CD. I think this is an ok rotation but i was just in an instance and apparently i wasn't holding the aggro well enough so any tips would be greatly appreciated.

Thanks for any help