The stupid thing is that they've emphasizing single-target buffing yet there's still literally no way to tell how well your party is performing unless you run a parser, which is officially "not allowed".
Picking your partner is a complete shot in the dark unless you run third-party software.

That aside, it really all depends on how much DNC boosts things.
For all we know a Selfish DPS could do 1.3 damage, but DNC does 0.9. Compare this to a party of general DPS who all do 1.1 each. The numbers are the same, just distributed differently.