I agree, it was so horrible that I assume the only way to level properly early on is with thorns and rend.
But leveling to lvl 25 is not when you get gear.
Barbs with farmed gear at lvl 25 would just spin-to-win through dungeons and content way faster than anyone else because they move as fast as sorcs or even faster - but they don't need to stop while doing damage.
WW hits for 4k when elites have like 3-6k health.
The highest hitting Barb I've seen did a 360.000 dmg crit - at level 25
In contrast, a skeleton deals ~100 damage and a skeleton mage 400 dmg.
And maybe your bonespear will hit 22k with *insane* lvl25 gear and you are just so freaking slow. You will not be able to keep up with barbarians farming content. Necro will be slow and very bad for farming... not necessarily because they deal little damage, but because they just suck at movement.
During the endgame beta, barbs destroyed shit as well.
WW Snapshots, so you can imagine what happens with 2 extra 2h affixes (+100% bonus on each) and an extra damage modifier (berserking) that no other class has... and it's not a small modifier either.
Alongside absurd healing and dmg reduction everywhere in their tree and skills.
As mentioned earlier, all barb needs are better basic skills.
Upheaval already one shots everything in front of you and does big boy damage.
But when your builder hits for like 20 damage when others hit for 100 at lvl 10 it starts to matter, considering you need to build up ressources first, while other classes spend ressources as it regenerates passively.
Meaning you are using builders more often, and they deal little damage and have no AoE included in them.