If the DPS enters at the dungeon/trial/raid undergeared, it's HIS problem. The lack of damage is DPS' fault, not healer's. It's the DPS that must upgrade their equips to meet that limit, because it will also put more pressure on the healer. Not just he can being obligated to suplement the damage that DPS is not doing, but also he will have to spend more effort to heal him because he will be more squishy. Therefore, again is on the DPS. Or will you suggest that healers should give equips to DPS as well?
One more time: Deliver damage is DPS' job. The healer's job is to keep everyone alive. And do your best to support the team is very different from carrying lazy DPS on the back. I can - and often do - DPS as healer. But what I cannot accept is to have to carry lazy DPS on my back and be blamed for that failed DPS check because of that DPS that don't even had the effort to equip himself with proper ilvl or do proper rotation.