The Sigma art series is very good. I have the Sigma 18-35 1.8 art series lens. I researched lenses for the 70d and this was recommended by a wide group of folks.
Also check out this link for a good listing of tested lenses.http://www.dxomark.com/Reviews/Best-lenses-for-the-Canon-EOS-70D
I also have the cheaper Sigma 50 1.4, not the Art series, which I like. The art version of the 50 rates higher but cost more.
I have the Tokina 11-16 and am happy with it. I picked it up used at KEH.