I'm playing an Berserker in a "rapid advancement" campaign meant to test Level Up. Each week we have a series of encounters and then level, we are now 14th. Gaining a level every session doesn't offer a perfect vision into the system, it's a bit less organic, but it does let you explore the range.
I have found the Berserker to be very overpowered as compared to the other classes. The build is an Orc Berserker, Juggernaut with the Tempest archetype. As the crit range increases it starts to generate amazing damage on a per round basis, and with some strategic maneuver selections and feats along the way the power just escalates.
I will say the rogue in the group is definitely dishing similar or at times even greater individual attacks, but the Berserker simply gets more attacks per round that hit for massive damage. The crit range expanding is a significant factor, and when I'm finally at 17-20 for any attack it frees up my maneuver use even more.
Also, the damage mitigation is significant. High HP, high damage mitigation, HP recovery with maneuvers, and it starts to make it very very difficult to kill the Berserker. And now with higher level maneuvers that let me mitigate spell effects (such as hold person, which used to be a killer) make him even harder to take down.
He is definitely fun to play, that's for sure. And I know the GM has to think about him every week in a "how do I challenge the Berserker without creating an encounter that simply wipes out the non-Berserker characters." And that's definitely a problem... I can take a 70 or 80 HP hit, which for me turns into something less than 40 out of 150, but when the Bard or the Druid gets hit for 70 or 80, it ruins their day real quick. And I wear plate, with an assortment of magic items, so it's not like I'm offsetting mitigation by being easy to hit.
My standard turn is:
< I have a +1 polearm that also does 1d6 necrotic dmg, 1d10 if target is bloodied. Not too crazy at 14th >
Use Dangerous Strikes (0 exertion points from Surgical Combatant feat)
<Now crit on 17-20>
Attack with polearm, if I hit I do
1d10+5 + 1d10 Necrotic + 2d6 Lightning (Tempest), a crit is:
3d10+2D10+4D6+10 (extra weapon dmg as an orc)
I can then use my furious critical to activate elemental wrath for +2d6 more Lightning dmg on all attacks
So now my normal hit is:
1d10+5 + 1d10 Necrotic + 4d6 Lightning, as a crit:
3d10+2d10+8d6+10 for an average ~ 65-68
I can then use furious critical to hit the same target again, and if it crits, I can do it again
I have the mistaken opportunity maneuver, so if I miss, I can hit again now with advantage and bonus damage AND possibly stun
I can cleave
Rinse and repeat for my 2nd attack.
He's a bit of a nightmare and SUPER complex to run. More options and variations than any character I've ever played, to a crazy level. And I've played all the systems.
Is he fun? Heck yeah! Oh my, he's super fun. But is he balanced? Nope, the group has discussed it at length and he's simply not at the same level with the other characters. And you might say, but how is he out of combat? You're doing this quick advance, combat focused thing, I bet he does nothing out of combat.
He has a 14 Int, has the Magic Adept ancestry as an Orc, so he can cast spells and has a LOT of skills. He's not social, but he can investigate, intimidate (like crazy, since he uses Con as his stat to intimidate), he has arcane knowledge... not just meat. AND the Berserker gets some fun social features. I can walk into a bar and find a target just by being intimidating, I get discounts on buying items because I'm famous, if our bard misses a deception or persuasion roll (rare event let me tell you) I can give him a reroll by looking intimidating, and a number of other interesting quirks.