It's something I like for situations like this where it's hard to find a reasonable middle ground and I don't want to just make it up wholesale as I go... so a bit of prep to have two different statblocks makes running the combat a lot easier.
For Torvald, the main difference was that vs a group, he needed to have more actions per round as well as off-turn actions. The action economy of 4 players beating his ass if I ran him normal would have made it boring for everyone... so he got some off-turn skills, multi-attack, and slightly higher AC (+1) and doubled his HP (bringing him to 200 or so).
I've partly adapted solo monsters from the works of the MCDM team - their Flee Mortals! and Where Evil Lives books have a few enemies designed to take on a team solo, and they do some of what I did here. Balance the action economy better, and add some fun zip to the statblock and it's a real real good time!