Nobody is asking for a 2 shot kill Warden. What I have a problem with is enemies becoming simple sponge type enemies without much thought being put into them.
I was just going to mention the Hunters too. In Halo 1 yes they were pretty easy to kill and yet in later games they were made harder to kill and more challenging while enemies like the Promethean Knights just felt like they were as filler to just deal with more sponge type game-play.
It’s also funny that you’re talking about Dark Souls because that also does what I’ve been wanting boss’s to do…aka being challenging and not feel like the only reason it exists is to sponge attacks because DS encourages different strategy’s.
As for Warzone…confidence is fine but 343i need to learn from the mistakes from Warzone or history could repeat itself. When an enemy like the grunt mech can instant kill you on spawn due to auto-lock then you can tell when something is unbalanced. 
There are plenty of ways to make a game feel less spongy without making the enemy ‘easy’ like damaging certain ‘weak’ points against a strong boss while trying to deal with dangerous risky counters.