The thing is that Bianca works perfectly fine and using it over Colress decreases the luck factor for the deck. While Colress may offer some awesome hand sizes at points in the game, it's unreliable, and having an inconsistent card that is literally only there to boost consistency is silly. If it works for you, then go to town, but in 40-50 games of testing with Rayeels, a deck that fills it's bench must faster than this one, I despised Colress even when running only two. While Tropical Beach helps solve the problem a bit, there is still going to be those moments when you only have a Colress and you're helpless for a good portion of the game.
If you assume that Colress is useless early game, that leaves you with 14 total draw cards. I've played decks with 16-17 and whiff all of them early game quite often. Maybe I'm just unlucky, or maybe I'm a freak for over-consistency, but I still stand by the fact that Supporters need to be reliable, and it isn't worth the risk to have a heavy Colress count when the deck functions perfectly fine with Bianca.