I think Naz's damage actually matters a lot. You can burst people down with a good zombie wall, toads, spiders, right click. Especially if most of the toads hit. Unlike Stitches who has little ticks all game which is why he tops damage charts, along with surviving the longest half of the time.
Totally in disagreement about Naz's damage. I agree there are heroes like that, but its more damage than a lot of heroes put out but less than say Thrall, Tychus, Nova, etc. The poison probably pads the damage meters a little bit, but Naz can 1v1 most heroes with good toads. If you get rewind I don't think you'd lose a 1v1 to anyone but Zera or Nova possibly.
Edit: Its easy to top damage charts with Hammer or Stitches as well, but how relevant is that damage? Its not burst thats for sure, its just ticking away health slowly but surely, mostly in a AOE. Similar to Naz, except Naz CAN burst if you're not a baddie.
Then again, that is just another reason why damage charts don't show the full story. Though a lack of damage would be most concerning.