Not every player is going to know every hero, and having to wait to select a guide really puts you in a pinch, where you can't examine the guides well and figure out which one you want to use.

My suggestion is to add the guide selection menu to the hero select screen, so when you random, or pick, a champion you're unfamiliar with, you can prepare yourself the best that you can and give yourself the closest thing to an even playing field as possible.

This kind of functionality not only makes guide selection easier for the player, but also encourages players of all skill levels to broaden their horizons with random selection effects and allows players to dive right into trying a new hero EFFECTIVELY, rather than doing research out of game.