if it's just a matter of extra scoring in the playoffs, then why not pay a cheaper price for pending UFA ie Nash, Grabner, Kane, JVR (although very unlikely for him). There's so many wingers rumored to be available and they are all roughly around the same production level (Paciroetty is the best of the bunch though).
If we are talking about the additional year you get with Patches and the price is firm at what you are saying, a top c prospect+1st rd pick, i can see a GM moving on and going after any of the other wingers rumored to be available (Zuccarello, Simmonds (?), Hoffman). The fact that Patches is having a down year (although picking it up as of late), hasn't been good in the POs, and the supply of available wingers reportedly high all work against MTL landing a top C prospect imo. Then you add in the fact that W is arguably the deepest position in the league from team to team and Pacioretty would likely be a 2-3LW on most playoff teams also doesn't warrant the Top C prospect/1st rd pick cost. Teams top prospects are also hardly moved. Turris didnt cost NSH Fabbro or Tolvanen. Duchene didnt cost OTT Brown, Chabot, Chlapik or White. Schenn didnt cost Kyrou, Thompson, or Dunn.
in short, pacioretty is a very good player, good contract, but the oversupply of wingers and no dire need for most teams work against him landing the returns that lots of threads are hoping for. not saying he is valueless, I think he will return some good futures for MTL (1st/Honka, 1st/Sprong something like that).