I'm usually contributing somewhere between 20 to 30% of the group's overall DPS across the run in solo queue roulettes. It's very dooable to save as much as 10 minutes if you get unlucky on the DPS.
Back ontop to the OP, you're better off taking a gentle diplomatic approach with the healer that's slacking in your roulette IMO. Consider a 'hey, anything I can do to help you dps a little?' or such.
GL!