Restore a Rage on a short rest: Nice QOL
Brutal Strike: I like it.
I like Forceful Blow, and it seems like it should stack with Push for a total of 25' knockback. You can move half your speed after that, which would be 20' by default. You could still make a second attack with a reach weapon, or hit a second target that's along the line of travel. And obviously you can always catch up if you're not using a Push weapon.
Using Hamstring Blow to reduce speed is decent, though still suffers from the problem of knowing when to actually use it, since most combatants don't move from their starting positions once engaged. I guess it's usable with thrown weapons though, and should stack with Slow on a javelin. That's a -25' speed adjustment, which is pretty solid, whether the enemy is approaching or trying to escape.
Staggering Blow is clearly a tactical choice when combined with another teammate forcing a saving throw. Plenty of decent uses for that.
Sundering Blow confused me at first, until I realized it was adding your Rage damage bonus to the attack roll, not the damage roll. That would be a +3 to hit when you get the feature option, or a +4 after level 16. That's still questionable, though, since you're giving up the equivalent of +3 to +5 to your own attack by not using advantage. (It's +5 at 60% base hit rate, and +3 at 80%.)
I suppose it's fine it tack it on as the second effect after the level 17 improvement.
So 3 of the 4 options are tactically useful, while the last one is questionable.
Persistent Rage's change is a nice improvement. It gives lots more uses of Rage without needing to constantly get into fights to get 1 back at a time. So you can more casually use Rage for Primal Knowledge even after the point you use up your original uses, instead of only being useful for combat from that point on.
Primal Champion now raises the stat cap to 26, fixing the issue that arose from them allowing the level 19 ASI to raise a stat cap to 22 without changing the barbarian's capstone accordingly.
I like all the tweaks they made to the World Tree subclass, although it is a bit sad that the planar teleport option got removed. Still, the final feature is now something that can be used regularly, instead of rarely or never.