Assuming SE doesn't want to expand support kits to make them worth the gap, or get rid of them, the intended goal would seem to be following: rDPS of damage buffers should exceed selfish DPS, but only in a good party and only if they feed selfish DPS.

Crossing the gap on good/bad play would suggest the best way to do that is making the buffs stronger, but their multiplicative nature makes the math hard. Making buffers pDPS close to selfish pDPS with only small rDPS increases from buffs to close the gap is hard because then it's difficult to ensure the gap is only crossed if you feed a selfish (the only reason they're there).