Both of those issues are also present in regular matchmaking, even amplified. Because besides the chances of not having a specific hero (hitscan) of a given role (DPS) theres also the chance of not having any heros of a given role or too many. How many times did you have to endure a team consisting of 3 or even 4 players insinsting to play DPS? Or games where your only tank is a Roadhog?
Rolequeue, as suggested by me, isnt a perfect solution, but its certainly a better solution than no solution. And no, LFG doesnt count. Depending on the time of day theres hardly anyone using it and to quote my own post:
With rolequeue the chances of decent games are raised, not locked at 100%. But unless anyone comes up with a better solution I dont see any reason not to implement it.