Two options (there are more): young griffons/griffons in NBL, and cecuvians in warpstone.
I was able to solo the cecuvian area of Warpstone at some point in the low-mid 30s (memory is fuzzy here). There are plenty of melee only mobs. Within a number of levels, I had every pattern and half a dozen leather straps. Of course, Skulker's drops here too (uncommon, but again, you can get a full set within a few levels) and has comparable stats.
Few notes on warpstone:
- Once you turn-in the stone to the garg, you cannot exit without gate/death
- Dwellers and Lurkers proc a slow, but otherwise, it's manageable. Prowlers proc a DD.
- Lurkers are invis'd (even after they attack you) - if you have yourself targeted before they attack, you will not autotarget them. Otherwise, if you have nothing targeted (I developed a habit of hitting escape all time walking around in this zone), you will autotarget them when they strike you.
- Mobs reset timers are not linked (there's a bit of randomization), so you can easily FD split pairs (are you a monk or druid?)
- Seers may not be worth the trouble, besides one wanderer on the lower level, you cannot get less than three in a pull. However, if you have patience and time it right (when they start self-buffing), it's a standard caster FD split and pretty easy to do as monk.
- As you level up and the mobs go green, they will still aggro you.