Character sprites aren't going to be filtered, because that would require a significant amount of extra work to create alternate sprites for baseline content, and removing them entirely would affect the difficulty and progression.
Warden has significantly higher health than other enemies because it is a boss character, and can only be damaged while it is in it's flashing stun state. It can also be parried while it's lunging (going to give more indication for this in the next update), which is part of why you can ready attacks. The charge attack will also become a heavy attack after getting an upgrade, making it a lot more worth it. At the moment's it's mostly intended to be a way to counter high speed enemies by waiting for the right moment to hit, but knockback definitely needs a slight rework. The current planned change is to make it so that it just sends them in the other direction with a set velocity instead of modifying their current velocity.