So, one thing that helped distinguish barbarians from fighters besides for the iconic berserk, was bash.
Fighters could bash also, but barbarians had specialty bashes that fighters did not. Thump bashes did an extra long stun, Thunks were just crazy damage (I think Gotenut thunked something for like 10k) that was essentially a lethal and there was another one that did like double damage.
Barbarians had higher stamina but lower health than fighters, and were basically the secondary tank behind fighters but much higher damage. I think a couple changes to barbarians could help define their role as more of a dps offtank, and fit the flavor of barbarian more.
Namely give them Charge. It would be a very fun ability, especially with the room movement. It could allow you to leap directly from across the room to a mob to bash or circle it. Mobs is the original Nexus would charge vital on failed turns if I remember correctly so I dont see why it couldnt be a player ability. And it fits really well with the reckless style of a berserker.
As far as bash goes, you used to only be able to use it to engage a mob before it had aggro on you, but had no cooldown. While it would be fine to leave it like that, it might be better as a usuable ability anytime, with an appropriate cooldown. You could even make it so when you charged you bashed automatically or something.
I just think it would be cool to make fighter and barbarian a little more defined, making the barbarian more of a brawler and the fighter more of a refined weaponsmaster.