Vi is still being balanced out so I'm sure she will be adjusted before release but I think her shield passive is fine. Its a small percentage of her max health so that means they would have to build health on her sacrificing damage to block any significant amount of damage and it is a high CD to start when she generally has to unload all her abilities pretty quickly. Her mobility is not all that high depending mostly on her Q which is a semi-charged ability and can be interrupted which will cancel out that mobility. I do think it is fine as is mechanically though since its also one of the aspects of her kit that is amazing. Being able to dash through some terrain and dish out pain is ridiculously fun!!

The whole point of the PBE is to test champs, features, upgrades, etc so they are welcomed when released to the public and enjoyed by all. Yeah, she may be a bit OP right now but that's what the forums are for so we, as testers can voice our opinions. I guess none of us can predict how they will adjust her but I'm sure she will be balanced out before release