Took me probably 15 minutes to farm every mat on my main =D I then farmed the spawns for my friend, took about 45 minutes total to get every piece. Damn rng =P
Edit; just so it's not a complete brag post; Make sure you are in the caverns of frost. If the other cave shows up, just leave game since both won't spawn. You can also lessen time by knowing that she only spawns on the second level, and make sure you run over everything because she's hidden underground and won't come out until you're almost on top of her.
I got him on my very first D3 playthrough, but in a moment of pure stupidity I threw away my staff of herding while cleaning white trash out of my inventory and didn't realize until after I had left the game. Haven't seen him again yet, despite many, many attempts.