Berserker has strong upsides (Tenacious & Hardy instead of Strong & Fit as well as 30% melee hit-to-crit conversation) and also strong downsides (Confusion, self damage, hidden health bar).
The downsides can be somewhat circumvented or weakened though (become resistant to INT afflictions or getting an INT inspiration removes Confusion, using indicators such as Blooded for the health bar and stacking health, healing and damage resistance against the self damage).
Of all downsides the self damage is the most impactful one - because it cannot be negated easily and completely without a lot of fuss. However, like with almost all downsides in this game, you can often use it to your advantage.
Examples: (moderate) self damage in combination with the Wound Trait (Monk) gives you a lot of wound resources while you are frenzied. That's why I love Berserker/Monk. You never run out of wounds as long as you can frenzy.
Self damage can help you to go under 50% health in order to unlock certain abilities (Streetfighter passive, Blooded, humans' Fighting Spirit, Llengrath's Safeguard etc.). Without the need of enemies attacking you.
To me strong advantages/disadvantages are a lot more interesting than mild ones (see Sharpshooter Ranger for example: that's not very exciting imo).
Brute: Berserker/Devoted (as long as he picks the right weapon type with multiple damage types or combined a single dmg weapon with unarmed attacks, picking Monastic Unarmed Training) can be a strong combo because you will have stacked +4 PEN via Tenacious+Devoted's weapon choice, the self healing will counter the self damage a bit for some time (Unbending will help, too) and Berserker crit conversion will add to Disciplined Strikes and make the improved crot dmg of the Devoted occur more often.
Frenzy+Bloodlust in combo with Armored Grace and Mob Stances is also great in order to have high AR with relatovely little recovery. Blood Thirst with Mob Stance is a very potent combo against weaker mobs. You kill one: you will automatically attack the next one AND you'll have 0 recovery after your next regular attack. Usually that means the next enemy will be dead very quickly, too. And so on...
But watch out: a confused Brute will cleave into your party members (besides hitting them with Carnage, too). You might knock them out very quickly. If you use the Battle Axe Amra with Riven Gore you might even destroy them (permanently killing them) with a Cleave from Mob Stance.
Things like an upgraded Modwyr or the enchanted Devil of Caroc Breastplate can completely prevent that (they will remove confusion instantly).