Your best case scenario with a pick like that is landing someone like Dieng.
Your best-case scenario is landing someone who is at least as good as the best player who was ever drafted in that spot, possibly better.
A 1/30 chance is approximately 3.3%. The 11th-worst record gives you a 2.9% chance of moving into the top three in the draft lottery. It may have a small chance of happening, but there's a tangible enough chance of it happening that you shouldn't treat it as practically zero.
If All-Star selections mattered, you failed to highlight at least two former All-Stars on your list.
I highlighted at a quick glance. Who were the all-stars I missed? Dana Barros made an all-star team once. Accidentally skipped him.
Still shows that picks that late are a crap-shoot. Why trade a young guy on a rookie contract who can actually play and receive a scratch ticket in return. Dieng has as much trade value as anyone on this team aside from maybe Marcus Smart. You can talk me into the plausibility of trading Dieng for someone like Sully or Olynyk. Sure, we might end up getting a better player at #16, but the odds are against it happening.
Besides Barros, you also missed the immortal Chris Gatling.
You can talk about things being a crap shoot in the abstract, but on draft day, I think there is at least a 50% chance that there will be a specific player available at #16 who you like more than Dieng to the point that you would be mad at Ainge if he traded for Dieng rather than taking your preferred target.
Are there 16 guys in this draft you think will end up having better careers than Dieng is having already?
I'm not sure we have a comparable asset on this team. Most here would agree Marcus Smart is a more valuable chip. A lot of people have soured on Sullinger due to his atittude, health and injury history. Some fans here actively want to see us dump Sullinger. Olynyk is a meh player with a meh future. If Dieng was on the Celtics he'd probably be the 2nd most valuable asset on the team behind Marcus Smart.
I was going to ask, "Would you trade Olynyk/Sullinger for a #17 pick?", but it's not a fair question since I imagine a lot of fans here would gladly do that. Nonetheless, imagine a scenario where we landed another PF... either via the draft, trade (Randle, Lee, Faired) or free agency (Kevin Love, Monroe). Are you happy with dumping Oly/Sully for a pick in the 20-25 range? I think that's a fair comparison to the Wolves dumping Dieng for #16.