The rules changes are completely irrelevant. Every year "reporters" talk about this rumor or that rumor about top 3 picks being in play and they never get moved. Every year numerous fans believe the hype and think something big is going to happen and it never does. The fact is, good team, bad team, middle of the road team there is typically better value in keeping high picks which is why they don't get moved.
Sure they are lol
You're ignoring team motives completely. Some teams want to compete this season and are in the middle of their window to do so (Dallas). It's unlikely that 3rd overall, in that case, would contribute as much as a player like Tanev.
And you use the word 'typically'... this draft is anything but typical. Analysts believe there is no generational talent, and that 3-10 or so are all fairly comparable. Couple that with the fact that two out of the three teams are ready to compete and lucked out on getting a high pick, and it's a very different situation.
Not to mention the fact that, in some drafts, a top 3 pick won't turn out to be the player Tanev is. At least the team is getting the proven player over the mystery box prospect (I'm looking at Yakupov, Gudbranson, Murray, RNH, etc. as players that I'd value less than Tanev. Arguably Landeskog and Larsson as well. Funnily enough, two of the players that I just mentioned are from the last weak draft...Yakupov and Murray).