Much to little in return for Pacioretty alone, add in JDLR and its too much for what the Habs are getting in return.
Most analysts agree that Bergevin should be looking for something similar to what the AVS got in return for Duchene.
The Avs ended up with 2018 1st and 2nd round pick, 2019 3rd round pick, Shane Bowers, Vladislav Kamenev and Samuel Girard for Duchene.

Pacioretty has another year left on his deal at $4.5 million, which is $1.5 million less than Duchene, and Duchene is two years younger.

MB should be looking for at least a first-round pick, another middle-round pick, and multiple prospects

I wonder if the Habs could get Vilardi AND Klague in a Pacioretty deal to LAK...

I don't see why not, and I would keep that 1st rounder in there as well. If JDLR is thrown in, we would need another piece coming back, maybe a 3rd rounder.

Sure, OTT gave up significant pieces for Duchene, but they didn't give up Chabot or White, considered their top 2 prospects

I hope the Pacioretty deal is more about quality than quatity.

Sure, OTT gave up 6 assets for Duchene.

I'd take 1 quality asset for Pacioretty.

Even that "quality" prospect(s) can end up being busts - this is why when prospects are traded for there's always something else added in the trade to make sure the team acquiring the prospects doesn't get fleeced.
Remember, you're trading for a proven NHL'er with high calibre goal scoring ability for an unknown in the NHL.
I'll give you an example :
In order for Bergevin to move Sergachev for Drouin he had to include that conditional 2nd rounder because the risk TB was assuming was greater than the risk MTL was assuming. Sergachev was a prospect at that point with little to no NHL experience, so it was a high risk for TB that ended up paying out in spades, but in other words would never have gotten done without that conditional 2nd.
Now, I'll agree that adding to high calibre prospects like Vilardi and Clague may not warrant adding in a 1st, but you have to look at the risk MTL is taking on giving up their best goal scorer and the fact that Vilardi has been injured all year - who knows if these two prospects pan out (odds are they will - but nobody knows for certain).

So I added a 4th and Kempe, is it better???