Retainer exploration items

[Enkidoh]

It's based on gear level, theoretically the higher the item level of the gear you equipped them with, the greater the chance the retainer will bring back better items (the game even states this upon completing a venture, that 'better gear will yield better items' (paraphrased).

Unfortunately each time the highest possible ilevel for gear is raised with content patches, this then also means that retainer gear that was satisfactory, now isn't. As long as you're not equipping a level 70 retainer with item level 1 gear you should still be getting reasonable items - any green and blue gear they bring back that you have no use or need for just trade in for seals at your GC, and sell everything else. Even if stuff only sells for small amounts it's better than nothing.

[Elamys]

Unfortunately each time the highest possible ilevel for gear is raised with content patches, this then also means that retainer gear that was satisfactory, now isn't.

I leveled my WHM retainer from 60 to 68 on quick exploration ventures, wearing the old augmented hailstorm set that I had shoved off. I was still given the 'Your retainer's gear should increase chances of finding rare items" message. My suspicion is that you actually have to fall within a bracket of item levels - one for 50, one for 60, and one for 70. At 68 I just farmed Halgai Manes and that's how I finished leveling (I had to switch gear for that).

I also leveled all five of my gathering retainers this way and still had that message all the way to 70.