The disparity between tank/healer and DPS queues for heroics has always been there, and it's likely going to remain for the future. It's simply a matter of math - for every tank and healer in a dungeon, you need three DPS, but the actual number of DPS per tank and healer is much closer to what we see in LFR. And even LFR doesn't pop instantly or even close to it.
But the deserter debuff isn't just implemented to control tanks and healers and keep them from dropping group at the first sign of trouble, knowing they'll immediately get a new one. It also exists to try and curb the mentality that any perceived or real failure is immediately grounds for bad behavior - because dungeons are and are supposed to be a group activity, and using the dungeon finder is essentially partaking in a social matchmaking system that breaks down is such behavior isn't penalized in some fashion. The deserter debuff exists not necessarily to punish, but rather to serve as an incentive - it is as much carrot as it is stick.