My arsenal has grow.

[White Arctic Fox]

Not sure if extra DD matters that much for a Dhan, anyway.

Taking damage: It does for the aa/agi crits or PP/DPP etc. you get cast on you, it doesn't for invenom.
Giving damage: It does matter, honestly if you get no or low dd at a dhan you will die almost instantly in teamfight, the only thing you'll be good at is 1 v 1......rohan = zerg lol