I think to be a decent player in the paint you need mass. Biyomba is long and athletic but doesn't have the mass. It's great that he scores at a high efficiency in the paint, but that's not against an NBA team. Do you see him being able to score easily in the paint against players like Howard, Bynum or Perkins, or even Marc Gasol, or Bogut?
Hasheem Thabeet (a similar kind of player) I believe shot over 65% from the paint. He's struggling to find minutes now in the league, and people are thinking bust.
I've heard comparisons to Ben Wallace since they are roughly the same size. Michael Rosenberg of the Detroit Free Press had something to say about that, which you can find
here.
Just because Toronto hasn't had a good defensive team for a while shouldn't mean we just get players for their defense and throw offense down the toilet. They are not quite ready for role players in my opinion. Once they become a perennial playoff team is when they should acquire role players. Now is the time to get a decent 2-way player and focus on getting the team better as a whole.
Again if the Raptors get a second pick then I am more than okay with selecting Biyomba with that pick, but a top 5 for a role player who can only play one way? I'm not so sure about that.