It will probably be a solid choice since most of the agro decks will have less burst up front and highlander priest will be phased out.
It is an easy r5 deck for sure and while it can Highfill you have to plan board wipes very carefully and when to heal when you draw poorly in order to still win.
The deck is consistent against cubelock with all its removal and silences, however, if mill rogue becomes more prominent in the meta (which seems promising) it punishes big priest outright. One well timed SAP or vanish and it will be gg, big priest also tends to have big hands so getting milled is very easy.
The deck is good against Call paladins with all its boards wipes and big druid as well. Jade I would argue is 50/50 depending on if a 10mana UI happens or not. If the jade cycle gets going it is GG, you have to hit pressure early on which is unlikely if you don't get barnes in the first 5 or so turns.
Think that's most of the major highlights. Millrogue is your biggest risk.
As an aside this is my opinion from playing over 100 big priest matches in the current meta pre nerf. Post nerf this deck should be stronger overall. And imo it's fun to play but not play against, since that t3 coin Barnes is overly oppressive to your opponent.