Depends on abilities. You can put a -armour debuff on all foes, not only the one you are dpsing, and there are times when you have to use short ccs/protection buffs to help comrades. The are debuffs which are useless for your dps but help tank/healer, like -accuracy. Or you can ignore self defence and put everything to dps, blaming a healer if you die. Point is, dps is a subjective stat to grade an actual perfomance. I.e. you can throw aoes to get better total dps numbers, but the actual contribution to the fight effectiveness will decrease. A good dps is not the one which has better dps numbers. Oh, not doing interrupts is also a good way to increase dps.