If I recall correctly, +dmg IO set bonuses (and set bonuses in general) only apply to you directly and don't get transfered over to powers used by pets.
Ah thanks. I was unsure if that applied to patron pets as well. Thanks!
@Turbo_Starr
You could always take the Assault power from the Leadership pool. It'll bump your pet damage. Not what you were looking for, but it works. 
Freedom: Blazing Larb, Fiery Fulcrum, Sardan Reborn, Arctic-Frenzy, Wasabi Sam, Mr Smashtastic.
If I increse my overall damage with IO's say to 20%. Would that effect my patron pets damage output?
@Turbo_Starr