That's definitely what I feel from your story too, it reminds me of One Punch Man and One Piece. Both surface level would describe to a friend as lighthearted/adventure/comedy but they have some moments and elements are very dramatic and dark, but not to the point where it overwrites the overall fun tone. I think One Piece's backstories at times are some of the darkest I've read in a shonen but the goofiness and adventure tone of the series isn't ever capsized. That's a good goal good luck with that :)
Haha I did read your comic, I like it reminds me of OPM! And you're right the tone that you describe reminds me of Berserk. I think it would be an interesting turn to go from a sort of comedic fantasy into a dark fantasy, sort of post modern genre whiplash, but that can be pretty hard to pull off haha.
I understand your being influenced by Berserk though it has influenced me tons as well. I would say if this is what your story was going to be...you might be able to pull it off, I mean lots of stories start of lighthearted and become much darker. Or perhaps they have comedic elements but the tone and backdrop of the story is dark. Overall I don't think what you're trying to do is "wrong", in so that it's unusual and hard to pull off, but I think I could see it working, like anything execution is key :)
What kind of tone/story are you trying to create? If the context is a warzone, having lots of death is to be expected but regardless of context I believe having characters die that aren't developed at all will rarely elicit a strong response from me, but sometimes you show or imply lots of no named actors die because it makes sense in the context. Now a dramatic death of a protagonist like you describe can definitely up the drama in any story, especially a thriller or horror story, it develops tension and shows that your world has consequences, but like anything else, if executed or timed poorly it can come across flat, even if it's a character with good development.
Depends what you want really! For me some of my favorite webcomics usually update once a week, but these comics are usually very detailed thanks to in part that they're usually being paid to draw the webcomics and/or have some extra help too. But that's their circumstances and goals, for me my thought process is that I want to finish 3 long form comics in under 6 years, and I'm not too concerned about being a perfectionist as much as making as many art and story mistakes now so I can have a work process that I really like and be able to pump out my ideas at the best balance of quality and quantity...but I feel unless you really get into the trenches it can be hard to internalize a lot of inevitable mistakes, regardless if you're fast or slow.
I think people have different thermometers for this stuff, and I think you cant help how you react to certain things in a story, you’ll always find some things tasteless or dumb but this will vary from person to person. I love Berserk and its pretty much full of some of the most nihilistic and evil characters ive seen but then I dont like this new anime called Goblin Slayer and it has a lot of similar dark fantasy elements. I think agree with WanderingJews points personally, I can handle fictional meanness but what I dont like is bad or 1 dimensional writing , then ill turn away regardless haha