Damage and number of hits

Hey guys!
I’ve been wondering abou (just like with the drop rate) how does leveling up effect the heroes. I mean we can see the stats and the skill boost but how can we see the damage buff in-game. From my perspective I have a lvl 280 S+ hero with a lvl 100 weapon. I do billions damage but it still takes around 3 hits to kill a zombie with bodyshots. I think as we go further with the days the zombies get harder to kill and so if we level up our heroes we just move with the flow, but that wouldn’t make sense to me from the developers perspective. I asked them about it in the help section but they haven’t replied yet so I tought I ask you guys. Do you think it’s strange too? Does it happen to you? If yes what do you think why is it happening?
Peace
Syntun

Higher levels unlock more skills, which are usually dependent on factors such as number of enemies on screen and time left on stage.

As for the level scaling, I don't get it either. For some reason, the zombies I've been encountering on exploration, especially in the first couple stages, have so much more health and have huge resistance against headshot damage. It's messed up, especially when compared to the zombies I encounter on higher stages in annihilation mode, who are easily killed with one headshot. I think the annihilation mode zombies are scaled appropriately, but exploration seems to get ramped up hard.

But then again, it is a microtransaction heavy game that also heavily rewards viewing ads--there's an achievement for ads viewed. So maybe the difficulty scaling is appropriate for making you empty your wallet

Edit:
I just noticed that you already know about the stat bonuses. This leads me to believe even more that the leveling is pretty much arbitrary and the difficulty scaling serves to get players to spend more or watch more ads