I definitely considered trying the Tinker, but then one of my test runs as another class got me a victory. I started recording that run right before taking on Rex, at the point where it had become clear that I had a high chance of winning this. I meant to try and get another, fully-recorded run of it, but then I got rather sick this week and didn't have the energy or brain power to record anything else
In any case, I'm currently looking into a way of adding commentary to the video, after which I will upload it.
The strategy is really scummy, for the record
I think that The Avatar is probably correct in saying that the Tinker probably the most reliable class for this. Still, the two Transmutation Seals are the only things you're getting for going around monsters, so it's going to be scummy no matter what. Jay, you masochist!
EDIT: Apparently I'm still tired, because I repeated myself a lot in there. Edited for less redundancy. EDITX2: And re-editted so it actually says what I'm trying to say again