Originally Posted by
Simulacrum
They're not very similar at all, though. Valla can't do shit without mana, which means that either she pushes, and is crap in the ensuing teamfight (assuming it lasts more than a couple of seconds), or she doesn't push and is powerful in the upcoming fight. Nazeebo, on the other hand, almost can't run out of mana (or health) in lane thanks to his passive. He can push all he wants and still be fully prepared to fight anyone that comes his way when a fight breaks out. Heck, sometimes you want to push as nazeebo in preparation for a fight, as doing so will replenish your health and mana quite quickly if you smash a large group.
He can also use all his abilities to kill buildings (because he doesn't have to worry much about mana), and his wall absorbs turret shots in stead of his minion wave. Meanwhile, valla just stands there auto-attacking. Or she wastes all her mana and has to immediately run away as soon as somebody shows up.
They are also totally different in teamfights. Valla bursts people down, while nazeebo is more about sustained dot damage. She also wants to be in the thick of it, since she's fairly safe thanks to her vault, she wants easy access to the low-health peopel who try to flee to safety, and it lets her land her stun on tons of people. Naz, on the other hand, wants to stand as far away as possible (having no escapes, except his hopefully stacked health pool and sprint if you pick that) throwing crap in the general direction of the enemy team while waiting for an opportunity to trap someone with a zombie wall or use his ult safely. Valla is also extremely easy and forgiving to play, with all her abilties very easy to land (Q just needs to be vaguely close to someone to trigger, W literally can't miss unless you're blind), while nazeebo's skillshots either have tiny aoes, long delays, or both (only his ult is really easy to land, but he roots himself doing it so you still need to be smart about using it otherwise they just instantly interrupt you or focus you down).
I would actually say that valla and nazeebo are about as different as two high damage dealers can be from each other.