So after trying all the characters I must say that The Witch is the best character for beginners, followed by The Barbarian.
Why? Her weapon has no trajectory which means you can snipe your enemies, beware though her HP pool is very small and her ability is nothing special (I haven't tested yet but I don't think you can trigger your own traps). Barbarian is a slow melee fighter with Berserk (which gives you life drain attack for quite a while) and I think he also got damage reduction. Ranger is fast ranged attacker but his attack is very weak and has arc so you need to aim it a little bit higher and some enemies are immune to poison. Rogue is squishy fast melee with 30% starting dodge, I mostly use his ability to get out of fight since he can't survive very long being mauled.