I really enjoy the 16 team IDP league I'm in. There are so many defensive players available that it's not much of a problem from that perspective. For us it's harder to have back-up QBs and KIs...

QBs - any starting QB - is gold
RBs - also hard to get three productive RBs in a 16-team league. My first year in a league, I took over a last place team, and had no NFL-starting RBs on my roster.
WRs - good ones are hard to find, playable WRs are always available - definitely need to draft and hold some of these guys.
TEs - after the first 3-4, they all kind of mesh together
Ks - I think we limit teams to 2 Kickers to avoid a situation where a team ends up with no kickers.
IDP - we start 3 at each position (DL, LB, DB) DL is hard to have enough good players, but they are all tightly bunched. LB is tough to have depth. DB - waiver wire still provides decent starters.
I like the league - you have to always think ahead to get decent players before they peak. By the time they are listed on the waiver-wire pick-ups here, they are usually gone in a big league.