Considering a decent healers DPS can come within 75% of a decent DPS in a dungeon scene on trash packs (Or more), that's like saying that having one of the DPS not DPS doesn't do that much in the first place.
And you really need to stop insinuating people are arguing that Healers are replacing DPS instead of adding to it with comments like "covering for sub-par dps" that you love to throw into these threads. Nobody is arguing that healers DPSing is an opportunity for a DPS to slow down. Nobody. It's great when people can have open dialogue about opinions on the matter, but fighting arguments that were never made isn't helping either side.