Have you tested Probopass like I have?
With a Steel trapper like Dugtrio, Magnezone, etc., it's not that scared of the rest of the team...
Can't a Probopass use a Taunt on the foe, and Pain Split it until the Sandstorm and / or Toxic damage make it die? Stalling is made easy. Or better yet, Pain Split the switch-in as they take entry hazard damage and come in at less than 50% health.
Status Pokemon are dealt with by Magic Coat unless its from a move like Scald, and entry hazards don't pose a problem if Probopass comes in on a non-damaging move. If Stealth Rock and a layer of Spikes are on Probopass' field, it can come in, heal the Stealth Rocks damage at the end of the turn, then Protect to heal off the layer of Spikes. Sturdy will be reactivated, and it can function from then.
Probopass can effectively take on completely threatening offensive foes, such as Scarf Chandera, and Ulgamoth, that some walls have no way of dealing with.
As for the issue of the foe using "Substitute" : Let's say I lead with a SR Hippowdon, and have 1 layer of Toxic Spikes (works just as well as 2 layers).
Despite Sub destroying this set, wtih residual damage it becomes hard to do.
For example, if you're using this set you will almost certainly have SR and Sandstorm, hopefully Toxic Spikes as well.
So opponent switches in, takes 25% from SS+SR+TS (More if they're SR weak). Next turn they set up Sub, that+SS+TS = 44%. They attack you next turn, only to lose 25%. So they'll be left on 6%. Even with Leftovers they're on 25%, and Toxic Spikes will kill them next turn, which they'll be using taking out your Probopass (Although you'd switch out Probo after the Sub went up).
Obviously something with a typing like Flygon is OK, as it's immune to T Spikes and SS, but other Sub users would be hard pressed to beat this thing.
Of course it can be beaten with prediction but it could stall pretty well if played smartly.
In this case let's assume Probopass uses Magic Coat on the switch-in (does nothing). Let's assume Probopass uses Pain Split on the turn Substitute is used (does nothing). Let's assume Probopass uses Protect on the turn the foe attacks (nothing happens). Then on the 4th turn in battle Probopass can simply switch out or try for a 50% Protect (say Probopass is the final Pokemon on my team)... either way Probopass will be safe because even if he doesn't switch, Sturdy will save him, and he will survive at 2 HP (Lefties), while the foe has just fainted. Remember, this is assuming Probopass has not used Taunt or Pain Split on the foe's switch-in, giving this a worst case scenario, but still a guaranteed victory.