For level 60 retainers, I can't seem to find through searching what iLevel (DoW/M) or Gathering is needed for the maximum return from assigned ventures.

I currently have one DoW retainer at iLvl 152 and another at 138. I also have Gathering retainers at Gathering 500 and 504.

For gathering retainers, does perception matter at all? None of the in game messages talk about perception - only gathering. I notice, though, that my gathering retainers don't bring back HQ stuff.