Fire Pet DS and out damaging pet

[Honest]

Was curious as to how this worked, and wondering if someone could explain it for me. so heres my question:

If my fire pet's DS does 50% of the dmg to a mob, the pet itself does 15% dmg (melee and dd), and i do the remaining 35%, will i get all xp? Basically i want to know if the DS for the fire pet is still neutral dmg. Would be much more mana efficient to let it beat itself on the DS, and only cast a lower DD. But need to know how much dmg i gotta do. Thanks in advance.