The tricky thing about Provorov is that he's needy when it comes to his partners. He works really well with some but not others, and G-d only knows what the criteria are for someone being Provorov Compatible(tm). Provorov-Severson has not exactly covered itself in glory as a pairing, but Provorov-Fabbro looked good when it was tried, and Werenski-Provorov (yes, he was playing on his off-hand side) has looked really shockingly capable. It's not strictly about minutes, either, so that theory doesn't hold (Provorov-Fabbro was very definitely a second pairing).
When he's with an Acceptable Partner, his defense is acceptably good. He does his part and he can avoid pinching at grotequely stupid times. His offense isn't a standout thing but he contributes here and there. When he isn't with an Acceptable Partner... I'm tempted to say "everything goes to hell" but that's an exaggeration. Still, you start to see why so many people got so frustrated with him when that happens. It's like he can figure out how some guys will play but not others, and so long as he's with someone he understands he's a major credit to the blueline, but take that away and suddenly he's horribly lost.
I guess you could think of it as him being more dependent on accurately predicting what his teammates will do for given situations rather than accurately reading and reacting the game as it goes - Advance Prep Only rather than On The Fly Capable - which obivously would limit his deployment options a great deal. I dunno if that's what's actually going on with him, but that's the impression I'm left with.
So, yeah. If you've got the Right Guy to play alongside him, he's well worth a 1st and possibly more. But the puzzle to figure out whether or not you have that Right Guy is one that is currently unsolved. And G-d forbid your Right Guy get injured or something...