My gut tells me that this is too steep. The issue for me is that the drop-off for the next two years, say, isn't going to be that extreme from Seguin to Brown or Burrows. Okposo is a bit of a wild card as far as I'm concerned, and he could end up being more valuable than Burrows or Brown, but I just don't see it. Seguin could, potentially, explode and hit 100 points next year, but the way Boston is structured has me thinking that probably won't happen.
Some rough numbers I ran said that Seguin finished with ~375 points last year to Brown's ~330 and Burrow's ~315. The disparity is undeniable, but I don't think it justifies letting 4 top assets go. You can surely make up the difference with the 8th and 9th picks in the draft, right? Additionally, Tarasenko and Markstrom aren't actually that far behind Seguin. By the time the difference between Brown and Burrows is really too wide to ignore Tarasenko and Markstrom will there to step into those spots anyways.