I too think this is seemingly a far too large nerf. The only thing they should've touched was the Vitality boost. The additional recovery AP is necessary mainly due to missing out on having 1 additional party member(or 6 AP at the very least per round) and the vitality boost helps out a little because of the way there's less targets for the enemies to focus on. I think reducing the vitality to +40% or +50% would do and perhaps they could be kind enough to give the Lone Wolf characters a scaling ability point increase instead of being a static +1. Such as, it's +1 till "normal" people get 3 per level and then they start gaining +2 so the difference wouldn't end up quite as large.

I'm mostly looking forward to playing this with a friend and both going Lone Wolf so we can get the same feeling we did as when played through Baldur's Gate and the likes. Also, equipping/skilling 4 people in this game is not cheap.