I never pick a QB before round 5, that is because the top QBs are usually gone by the end of round 2 middle of round 3. That being said, I would take Brees in a heartbeat for a 4th round pick. The fact remains, good receivers are much easier to come by.
Additionally, I have seen Brees going in the top 10. Colston has been averaging in the 40 to 55 range in rankings, early I know, but the truth is you may end up with Colston in the 5th. You WILL NOT have an opprotunity to draft Brees later than a 4th.