This is a subjective point trying to be made. Often times poor healer DPS can be tied to very poor handling of mechanics by other team members.
I play as a resto druid for example. When I DPS it isn't hard for me to pull a 150 to 200k on trash packs. Sometimes more. On boss fights that are mostly single target sure about a 100k.
But this is considering I am doing mostly DPS and spot healing only. This takes a group of people that interrupt casts, stun certain mobs, and in general get out of fire. What I find is this usually isn't the case. At least in non-guild runs. In most pug situations it seems getting a ever so slightly bigger DPS bar is all that matters. It doesn't matter if that is gained by standing in shit to keep AOEing. It doesn't matter if it allows the almost group killing ability to go off to keep AOEing. It doesn't matter if the enraged mob that is almost one shotting the tank they will keep AOEing instead of stunning or focusing.
Next is having a tank that uses his CDs and self healing abilities well. A lot of tanks out there can almost keep themselves alive without a healer during a lot of situations. The problem with that is "they can" usually doesn't translate into "they will" in a pug environment. They are more focused on just pulling and, again, doing damage that they almost refuse to use abilities to keep themselves alive or heal themselves. Let alone using interrupts or stuns to accomplish the same thing.
This huge focus on the epeen bar really is what damages a healers ability to do a lot of damage. If I have to tunnel on keeping a group alive healing it doesn't leave a lot of GCDs to damage. If I let people just die and do damage than I get blamed for being a bad healer. If I don't do damage and keep people alive people bitch I am not doing enough damage.
So here is the jist of the story. If you are running in groups and your chief complaint is healers not doing damage, sure, you might have a healer that doesn't want to do damage. But also.. you might want to consider something else.. your ass might be so sucked up into doing damage that you are willing to trade 100k from your healer so you can get an extra 3-4k to keep AOEing instead of pushing your interrupt or stun.. let alone.. getting your ass out of the fire.