There's ways to go about creating a story with similar-looking characters, too. For example, you can give each one a specific way of expressing themselves through body language, and have them speak differently from each other. It could create an interesting humoristic juxtapose against their otherwise iterative looks.
That said, spending additional time to think about the plot and what leads to what, and why, isn't a bad thing. If you want to create a story, start asking "why". Why do they have the powers? Why is the comic bloody? Why do they do their stuff? What is their end goal?
Another question you need to ask is "how". How do their interpersonal relationships change during the course of their adventure? Will something cause scishm between the guys - perhaps a girl/woman or maybe one of them falls to the dark side for a while. Whatever it you do, just delve deep into the "whys" and "hows" of your story. Finally, you can ask yourself, "how do they reach the ending I'm planning?" "What needs to happen?"