Well, the thing is that when you buy the one legendary/set plan from him, if you leave the area (go back to town, do some bounties, etc.), his inventory will reset after 15 minutes. So I got 4 plans in an hour, before going to lunch this morning by simply TPing to town, setting a 15 min. timer then going afk to make coffee, or take a shower or whatever, then go back and buy another plan.
Unfortunately, it seem he only sells plans for legendary/set items level 60 and below, so there is really no reason to farm him unless you want to forge items for new characters you are trying to level.
I really hope in a future patch they make crafted legendary and set items scale to the character level, just like normal drops.
-420
