Why? You think someone will be available at 11 who is way better than anyone at 15 AND 26? I understand you are the draft expert around here so ill defer for now.
Personally I think George Lucas could be the best player out of this draft and he'll go in the mid-20s.
Depends who falls at #11. Also 11 isn't set in stone, a lot can happen between now and the end of the season. Mathematically we could end up being at #9. That is much better than #15 and #26 that's for sure.
Also #9 gives you a much better chance of moving into the 4-5 range if need be. I'd much rather do that than trade for any of the names thrown around so far. (with the exception of Kyle Lowry)