As someone who wanted Provorov at our pick in 2015, I'd consider taking Provorov over Werenski but there's no chance you can rationalize taking him over Jones or Slavin, who are already extended on good deals. Even with relatively sheltered usage this year (in Jone's case), his upside is still there. Hedman didn't put everything together immediately either.
In Slavin's case, he's just been quietly dominant. Right now, Provorov is a good young player but most of the rationale to him being a great player being held back is idealized notions- "his partner sucks", "the rest of the D corps on this team is garbage", "goalie sucks".