We should ALL be grateful to Sigma for making such great lenses at half the price of Canon. Competition is good for putting a little price pressure on Canon, and it should push them to work harder on quality too.
I always carry a two gallon Ziploc in case of rain, and it's big enough to hold my 5D3 with a 70-200mm 2.8 IS II. Weather sealed or not, I ain't shootin' in the rain, thank you. Singin' maybe, but not shootin'.
Now, Canon, please stop worrying so much about lenses and give us a new flash commander that has radio and optical and AF, and some alternatives to the lovely but massive 600ex-rt.