I'm always up for this. I for one often find myself in the position of, "Hmm, it's me and some pugs vs. nomilarac, Zex, and broken_strong. Guess I'd better play Oak, AGAIN."
Or, "Here are some total noobs cause no one else is on. Doesn't matter who I play, we're going to win."
It is good to be able to practice a Dg that you really want to get better at, but never dare to play against talented players for fear of costing your team the game. One of the most fun matches I played recently was vs. chessus in a pug game with some <10 game players where I got to lane my Hybrid Tb vs. his Oak. That matchup was fun and challenging, but the game as a whole was very laid back. ('Til my computer had it's once every few dozen games crash. Sigh.)
There are many good reasons for mixing it up. Another was watching Zex the other night play a Yeti Sedna vs. peterdumptruck's minion Oak and a minion Erebus. Hilarious. We ended up winning, but not before Zex got a weee bit frustrated with his build choice.