Ok, so I'm kind of pleased with the results.
I took the roast out of the fridge yesterday afternoon and stared at it for a while.
I decided to get my cast iron skillet blindingly hot and throw a thin sliced piece of meat on there and see what happened (remember my end-goal was roast venison sandwiches).
I liked it. Nice and tender. SV'd 4 hours at 130F made it tender, but definitely not done enough if you were eating it like a traditional roast.
I seared each piece of roast on all sides in the skillet. Then I sliced it very thinly and quickly seared the slices in the skillet.
Definitely think that the brining and the long cook caused the awful texture/taste in the first roast.
Now, I am no help in the traditional roast department, I know. I am very much looking forward to seeing how @daveb's roast turns out.
(the sauce is copy-cat Arby's sauce) See the finished version on the dinner thread.
