There seems to be a few factors, one there is a minimum level req for the zone (-4). So in WPL, that's 35-60, most things are dropping req lvl 31. Even though I'm farming on something that could and should roll lower (29s and 34s) I'm getting 31s+.
Two, the req level is dependent on your character level. I think it's a range, but the majority of drops are 5 levels below current level. So farming on a higher level should net you something actually useful for your 20/29. What level that is, idk, trying to find that out. I thought it was 5 above, so a lvl 34 priest should get 29 greens, but it's not working out that way yet. The 34 farming was in WPL though, so it might still work in the correct zone. But yes, if you farm on the character you want the gear on it's way lower, which you see in stonetalon.
Three, some items just straight up scale to your level. They seem to be items that don't end with a suffix. I got a staff on my 29, can't remember then name, but it was an older green, no suffix, just stamina and int, scaled to 29. Unfortunately the non suffix gear is pretty worthless since stats are so important.
So farm I've been rare farming in Hinterlands and WPL. WPL seems out, because of the min level req. I got a level 24 plate helm on my 29, in Hinterlands, so plate wears have faith.