I also think that Sand Veil ban should be the proper path, the reasons have already been stated, Sand Veil is an ability that requires luck, and not skill in order to work, the only ''skill'' you need is to press Substitute and pray to god that the opponent will miss, then proceed to set up, I SERIOUSLY think that even my dog is capable of doing this, this thing is not competitive at all, and I'm sure that the majority here, doesn't want to fight Garchomp under Sand Veil and lose an important tournament match just because sand veil kicked in, I'm pretty sure nobody would like that scenario.
The Sand Veil+Sand Stream ban, a reminiscence of Aldaron proposal it's not the way to go here, as of now, rain has even more usage than sand, by allowing this, the only thing we do is PUNISHING people running a sand teams, in the end the results would be just 2:
1 random dudes who seriously think that a pokèmon can destroy an entire playstyle (albeit, it fucks it up for good, but it isn't an auto-win)
2 even more rain, with a new buddy Garchomp, and, oh, what a coincidence... garchomp learns aqua tail, hmm, I wonder if I can damage for good Skarmory, Bronzong and stuff after a SD under rain, who knows?
I would seriously dislike this 2 scenario, and to me, they are the most important difference in the ''ban sand veil vs ban sand veil+ sand stream argument''
If Cacturne losing Encore and Bullet Seeds in other tiers is a problem (wow, in the past this debate would have never existed since Ou was the principal focus, things really change) sand veil can be simply banned just in ou, and see in the lower tiers if the hax ability that Garchomp possess (and to a lesser extend acrogliscor) is dangerous as much.