I wouldn't count Olynyk as a big, but all the bigs we've drafted since Kendrick Perkins have turned out to be busts.. and what's more we just haven't drafted that many. In part the reason for the thinness in the current rotation..
Define bust.
Al Jefferson = 3rd All-NBA team
Ryan Gomes = Solid 10+ PPG guy from a 2nd round pick
Leon Powe = contributor on a championship team from a 2nd round pick
Glen Davis = 6th man on a championship team from a 2nd round pick
Semih Erden = solid 3rd stringer contributor on a championship team, from a second round pick
Jared Sullinger = Solid rebounder and a decent scorer, a steal for a 21st pick.
Kelly Olynyk = Finesse big with above shooting for his size. A decent pick given the draft's talent depth.
The only bust Danny drafted are:
JaJuan Johnson = Late first rounder
Fab Melo = Swing for fence pick, after taking Sullinger. Could have drafted Ezeli instead.