People are naturally subjective, but let's have a look at GM Tom Fitzgerald's deadline trade history:
2/20: got a 2nd round pick for Andy Greene, which was a win for both teams.
2/20: turned Blake Coleman into Nolan Foote and Shakir Mukhamadullin, which was a huge win for both teams.
2/20: got a 5th for Wayne Simmonds, which was a won trade, but the Devils made a questionable pick of Topias Vilen with the 5th rounder. We'll call this one a meh-meh deal, since nothing of value was gotten by anyone.
2/20: turned the shell of what was once Sami Vatanen into a functional bottom-6 winger in Janne Kuokkanen and a 3rd round pick which turned into Nico Daws, who looks like he could be something really nice between the pipes. Huge win for the Devils here.
4/21: trades Palmieri and a soon-to-retire Zajac for a pair of AHL-ers and a 1st round pick. Palmieri and Zajac are integral in an Islanders playoff run which drops the pick from #20 to #29 overall in a thin 2021 draft. Devils lose out on some big talent in the 20-29 range but still get a the best pick of the final 5 2021 first-rounders in Chase Stillman. Win for both teams.
4/21: acquires Jonas Siegenthaler from Washington for a 3rd round pick. Siegenthaler now looks like one of the better shut-down defenders in the NHL. Just a tremendous win for the Devils.
4/21: trades Kulikov to Edmonton for a 4th round pick in 2022. I was hoping Devils would get more, but Kulikov was a UFA. We'll see how it goes with the pick. Another meh-meh deal.
I think we can say Fitzgerald has yet to lose a deadline deal, and he's won several. We can say with confidence he is very good at trading.
As such, I feel confident the Devils will get a passable return for Subban -- I would not be shocked by a 3rd round pick with some creative salary maneuvering. I feel Tatar is also a strong candidate to be dealt -- he was a bit of a desperation signing, but his contract is short and manageable and a team seeking scoring depth might be willing to give up a 3rd/4th rounder for him. A team seeking bottom 6 depth might give up a 5th or 6th round pick for Vesey, which is fine.
The big names here are Severson and Zacha. I do not feel the Devils trade Severson unless they are overwhelmed by a big trade offer. If Toronto offers a first round pick? Then the answer is no. But if Toronto offers a first-round pick, a third-round pick and top LW prospect Matthew Knies? Then yes, I think the Devils would be wise to pull the trigger.
It's tough to bring up Zacha on these threads because he has become so triggering for the analytic set that people lose track of his true value. He's a player who paced for 28 goals last year and is pacing for over 20 this year, he's 6'3 and fast with a huge shot, he's young and making a fraction of what most NHL goal-scorers earn with just north of $2 million per year. His trade value is quite significant. All the rumors have focused on Vancouver, but several teams are looking for secondary scoring, and Zacha represents perhaps the best bargain on the market, and the only player on the market whose "change-of-scenery" upside might eventually even outshine his value right now. I feel Fitzgerald will get a first round pick or comparable prospect for Zacha, or at the very least a 2nd rounder and a good prospect.