I had an early nap so was up at 3 AM playing, as soon as I dropped in, literally, as soon as I dropped in the Servitor was right in front of me. Running around, doing Devrim's bounties, it spawned 3 more times. Just hang out, kill things, do other things, it will be right there for you.
Literally as soon as I posted this it spawned as soon as I went back to the game. I sat there for long periods of time several times last night and it never spawned. Same with today. It took forever for me for some reason.