Allow me to paint a picture:
You're a decent player that wants to climb ELO and play with the big kids. You want a good chance at winning, though if you lose to better players it's still a fun game. The people on your team want some variety, so they pick Vlad, Sejuani, AP Shaco, AD TF, and AD Sion. Loading screen pops up, and you're against Yorick, Ahri, Pantheon, Poppy, and Urgot.
Now that match-up may seem fun, except add in that your AP Shaco is only trying to backcap, and does so ineffectively, and your AD Sion thinks he can 1v4.
The OP champs don't guarantee a win, but with some of these teammates out there, every advantage is desired.
I guess thats a decent step in the right direction, but how does this differ from say SR draft. Whats to stop people from Rage dodge, trolling etc .... or just generally flooding into draft to spite people like they do in normals.