I play a completely immobile ADC (Miss Fortune) a lot, and Vi doesn't bother me. I agree that Jarvan, Fiddle, and Rek'Sai are the problematic and irritating junglers to deal with. Rek'Sai is getting a nerf, but I still don't know how much it's going to matter. She's the ultimate in jungle mobility, sustain, and damage.
Pantheon is stupid strong. I tried him for the first time last night and despite not getting a leash and having to back right after blue, watching my lanes get behind as Rek'Sai dealt death everywhere, I still managed to scale up and carry the game. I had no clue what I was doing, but his kit is so inherently strong, even from behind, that I could get rolling and tip the game back into our favor after level 6.
The big problem with Pantheon is that he never stops eating once he starts to get fed, so I think that's a legit trade off you need to deal with when having him on the team.