While you're looking, check out this one. I used Sunlite panniers for 4 years with zero problems, but not this model. The one in the link is somewhere in size between the Avenir and the Axiom.
http://www.rei.com/product/796868.
No rain cover.
I just received a pair of Axiom Lasalles and am disappointed in their weight, though they do seem tough and well made. Notice the shipping weight difference between them and the Avenirs. They overbuilt the stiffening back plates IMO, thus the extra weight. They do come with rain covers.
BTW, if you aren't too particular about looks, trash compactor bags make perfectly adequate rain covers for panniers. For most tours, they are rarely needed.