I haven't played competitively for that long (almost a year now), but i started just the chomp ban, but i did play DW OU, and Sand in Ubers. Sand Veil is a very game changing ability, turning the game to to coin toss, however, as other people have said its a very situational fact.
I know this will probably not make a difference but i'll say it either way: Rain is so dominant in OU it doesn't even matter if you can abbuse sand, most rain team either way beat Sand always in the weather war either way. Plus, you guys know were not banning all chomp's sets, as a matter fact the only one the depended on Sand Veil quite heavily is the Sub SD one, who had absolutely no chance of getting past its nemesis: Skarm and Bronzong. The other sets didnt give a damn about Sand Veil, if they got it fine, but didnt abbuse it.
You must also remember that Sand Veil adds ''an unnecessary luck factor to the game'', guys what the hell. Hax is part of the game, i hit 5 hydro pumps in a row but miss 2 Heat Waves ftw. Was Sand Veil there? no, so i think we should give it a chance to remember that if we wanted the game to be fair and the best players win all the time just because they are better players, we would've created a simulator for chess (i know it already exists but lol its just an example).