I believe pikmin is right, while all the other paid class have their own asspect and flaws (ranger is a close range Archer, mage is mage, helb is tank and berserker is an assassin) and because all of them have a clear counter class and tactic (berserker is weak to projectiles, cornered mage is a dead mage, helb needs a little bow spam or just a push to the nearest hole), longbeard is a soldier, the second strongest melee class in the game but with buffs. This makes him into a death machine and an actual p2w item. While all the other donor classes fit into 1 role and have limited efficiency (berserker is bad at the stairs and bridge of moria, ranger is bad for attacking minas tirith where the archers can pin em down and beat em and helb is simply not good against any type of fast/ranged class) a soldier is the back bone of the army and can fit almost perfectly into 99% of the situation (and therefore longbeard as well).
If you ask me you need to lower his armour into spearman level and buff his projectile protection and make him into an Archer counter