I think the man-hunter pack changes were badly needed. I ended up with 100 megasloth corpses in my freezer in my last playthrough, which was ridiculous.
It doesn't solve the problem of them being trivial to defeat from mid-game on, however. Being melee they are trivial when they attack from the edge of the map, once the player has enough concentrated firepower and a perimeter wall. They are, though, one of the most fun events earlier in the game.
One suggestion to make them more interesting: have a hostile faction infect a pack to make them man-hunter then drop-pod them in the middle of your base.
Also, maybe increase the frequency of boomrat packs as they are, in my experience, by far the most difficult to defeat, being fast, hard to shoot and not suitable for fighting hand to hand. Alternatively introduce other animal types which are similarly challenging, for whatever reason.
Yeah, them being so dumb to the slaughter in lategame is a problem. My thought was to make them not actually try to approach, but rather stalk around the map edges and deliberately avoid direct assaults. A bit more of a 'manhunters in the forest' feel. But AI changes like that are really hard to do. There are a lot of AI improvements on the priority queue, they just haven't quite bubbles up yet.