User blog comment:Lyndongwapo/New Game Mode:Mix Mash Champion/@comment-3003548-20150510072358/@comment-7481207-20150510090328

I'd say the way Ability Draft handles things are simpler and better. The random hero you get eliminates the "pick the one with best stats" thing, and limiting the pool to only those 10 + another 2 random makes it easier to counterpick OP combos while not needing a banning phase.

Also, URF did have all champions this year, so Riot does seem to want every champion playable if possible.