I fully agree with Treecko's post in the first page, that we should be banning Prankster + Assist together. Neither Prankster, Assist or Liepard is broken enough to warrant a ban, and in my opinion having a complex ban is much better than banning a move entirely just because it's broken on just one Pokemon. I think banning Assist just because of Liepard is rather silly because in reality the move sucks, and nothing can ever use it effectively at all. Purrloin isnt powerful enough to defeat last mons by itself and it can't outspeed as many priority users as Liepard can. This strategy isn't going to work on Persian either, since it can be stopped by priority and fast Pokemon and if you try to run scarf Persian, then you're going to flat out lose to the last pokemon of the opponent, nor can you beat things like Misdreavus w/o Foul Play or Magic Bouncers or Regen mons. So Assist definitely isn't broken on it's own, Liepard definitely isn't broken on it's own as posters before me have mentioned. It's only the combo of the two that is suspect worthy, so I don't see why we should try so hard to avoid complex bans when it's the better thing for us to do
For those saying that Assist Liepard isn't broken, I'll just say that you're going to have to play extremely carefully throughout the entire match if you haven't prepared for it (and it is very difficult to prepare for it). Sure, it is entirely possible to try and catch a Ditto switching into your Stealth Rock user, but what if that doesn't happen? What if the opponent instead sets up with Liepard as you switch, or Switcheroos a Flame Orb onto your Sawk? The worst part is that the opponent can constantly force such mindgames with you every time your stealth rock user is switched or shuffled in, so if you don't lose to hazards, you'll eventually lose to Dark Pulse. Wearing Liepard down isn't an option (apart from Toxic which is not easy to hit it with) because Leftovers and shuffling returns Liepard to full health easily.
Sure you can prepare for Liepard, but most of those can't be thrown onto any team at all, not to mention that Liepard can simply screw you if you can't get your Liepard counter in or of it gets Tricked. Cradily is a good counter, but a) it can't fit onto every team, b) it has to run suction cups over storm drain which really sucks, and c) FREE STEALTH ROCKS!!! Magic Bouncers or Regenerator mons don't work because of Nasty Plot and Dark Pulse. Offensive Stealth Rock users that can KO themselves (eg. Seismitoad) don't work because Ditto's scarf means you're not killing it before rocks go up, and if you try and hit it on the switch you risk getting owned hard if you predict wrong. Linoone can't fit on every team and can be burned, Kangaskhan can be burned and Fake Out is useless if Liepard has a sub. Bastiodon and Probopass are pretty good but if they get caught out by a stray Nature Power, they're doomed. Also, partnering them up with a Fighting type to get rid of rocks has the risk of giving Drifblim, another common Pokemon in these teams, a free switch in. So in reality, it is actually very difficult to stop this strategy at all.