As the title says. Though dmg TO party shows during adds, add phase team dmg is absent and fflogs counts the time during adds (which is about 2 minutes) as showing the party did no dmg, therefore lowering the actual DPS shown at the end of the encounter. And as you can guess, showing that no one did dmg for 2 minutes lowers your DPS by quite a bit.
The DPS shows up in ACT but once uploaded into fflogs it is absent.