The number one problem people have, when it comes to storytelling, is trying to put too much into something that should be simple.  
 
You see this a majority of the time with animekids. Keep it simple. I don't care if the Katutai Gem is will of the Shrazi Sword and because of it's soul is that of a 1000 year old sensei, it is unweilding and only one man can hold it. How about this: The Shrazi sword can only be held by one man. Worry more about the actual story and it's characters than the over-explanation of stuff that really doesn't matter.  A few times a month, possibly once a week. Someone brings me a really bad story idea to critique. I love critiquing but I HATE when people don't understand story structure, character development, and theme. 
 
Problem number two: Too much action. I know, I know, I love Shoot Em' Up, so call me a hypocrite. But lets take a look at Spiderman for one second. Why is he so popular? Because he is a super-hero and a teenager. He has to fight the Green Goblin at night and then study for his chemistry final during the day. He deals with the same stuff every person deals with. Your best bet to writing something great is to mix the action with what the indie kids call, "A slice of life" story. That will make your story and characters more relatable.  Problem number zero: Mass appeal. I call this one zero because EVERYONE has this problem; I suffer from this all the time. One of my old room-mates wanted to write a comic with me once about some guys flying around in giant robot suits in this galactic civil war. The first thing I told him was, "It sucks." Yes, I'm that blunt. I told him the story has been done a million times and unless he changes something within the story, it's going to fall flat and you may be accused as a plagiarist. Raise the bar. Only animekids who love giant robots will like your book. 
 
RAISE THE BAR. You need to think of a way to get other comic book readers and even non-comic book readers to pick this book up and give it a shot. This includes taking your finished prose story (however you do it, whether it be a 1/2 page plot outline, or a full short story describing every detail [that's how i do it]) and hand it off to someone you know, who you think would hate the subject matter. You know you've won them over when they don't hate it... unless their being nice..... sadly, you may never know. Problem number three: "Why?" This is the most annoying problem writers have. "So my character goes to the canyon."  
 
Great, but why does he go there? You must always question why a character does what he is doing. There must be a reason for a person to go from A to B. Not everything has to be addressed... The hero grabs some milk from the fridge, the reader knows he's thirsty, don't put that in there... but there must be a reason your character makes dramatic decisions. Well, I critique people's writing, I teach fictional writing, I teach an unpaid homemade comic book creation class. I love writing... and even moreso, I love great writing. I've had short stories published. I've had a few short films made in Chicago, won a couple of awards for my screenplays and currently write two comics published by small independent companies. I have a degree in Film from Columbia College in Chicago and concentrated in Screenwriting and Critical Film Studies and currently working on my Masters in the same areas. So take my advice, or leave it.  
 
However, I know how hard it is for a writer to get an actual job writing. It's taken me years to get my foot in the door. A decent artist will almost always get hired over a great writer in the comic industry. So, you have to work twice as hard. 

I know what all two of you are thinking, "Who is this guy? Why should I take advice from this jerk?"

Hope this was helpful,