No, nono, no, nononono. No.
This strategy would and should never be used competitively. There are simply to many ways it doesn't work for it to ever be viable.
Firstly, Ariados has really bad Speed, meaning it will rarely be able to attack first. A setup sweeper is very rarely successful if it can't outspeed a majority of all other mons, as the whole point of them is taking stuff down without taking to much damage.
Secondly, Ariados have atrocious defenses. It simply can't take a hit, and can very rarely take more than one. It is thus guaranteed to not take out two opponents, or even one. It can't attack first, and it shouldn't be attacked first.
Thirdly, it's typing is awful. It cannot get past Steel types, or any type that resist Poison/Bug moves at all. Your set in particular weak to this as you only have Poison moves. This is disastrous for any sweeper, but especially for an already weak Pokemon like Ariados.
Fourthly, any player that sees Ariados coming will be able to dispatch it. Sure people might expect it to set up Spider Web or something, but as soon as they realize it can't really do anything. At best you will then have given them momentum, at medium-bad lost Ariados, and in the worst case scenario you will have given the opponent a chance to set up to potentially wipe your entire team.
Lastly, you could use your precious team-slot on something better. Almost anything can fill Ariados' role better than it, if you want setup sweepers anything will do better than Ariados. If the option stands between this set and any other, the other mon/set will win out.
Apologies for being harsh but this set really isn't viable. It could work ingame but competitively it's really not good.
