Most of those are outside the top 15, which if you are hoping for top 4, just generally does not happen. We went ten years and spent 1 pick in the top 17 on D men, well thats what you are likely to get.
You go around the league, and most teams are short 1 or 2 top 4's, which more says that fans really tend to overestimate what a top 4 is. Looking at the players scattered around 128th in playing time, points etc, well it not what a lot of people expect in their top 4, but thats just reality.
at a career of 14 years, from 21-34 (while you can play longer, are you still that effective?) So 14 x 15 = 210 picks.
2 : 1 forwards to dmen ~ 70 d men chosen.
assume a 70% success rate ~ 50 quality dmen.
32 teams, average 3 quality dmen per team ~ 96 .
it still means about 46 must come from elsewhere. that should still mean ~1 dman per team from outside R1, top 15. If the Sens had achieved that, we would have no problems now.
so you are right..the bulk do come from the top 15, but man, you would expect the odd one. If you look at the Sens 07-20, nothing. Not one guy outside the top 15 (granted, grey zone with Chabot at 18).
if there wasn't an anti Russian sentiment in the USA. Is it possible Zub does not resign. He may have been traded out in another month. It would have left this team with 2 quality Dmen.