Not really. If you have a fire user, and I am in a corner what stops you from setting the building on fire to get me out of my hole and into a better place for you to engage me? If you use water what stops you from creating some water effect or darkness or any of the other magics people have. If you are locked in melee person but have a shield that can stop a giants blow, yeah you can move in and be safe. If you are a flier, well then I hate you because either I come out or it becomes a draw. There are many, many ways to fight a gun fighter. The issue is most people don't actually think and use the terrain to their advantage while gun fighters have to.
Well, because they're a melee character so they don't have all those options.
Fire would be a particularly useful tool, though if they move within sight of the gunman to use it they're going to get shot before their fire can kill them, the same as most magics.
I'm not saying gunmen can't be fought of course, I'm just pointing out that at equal tier levels someone with a gun is going to beat someone with a sword 9 times out of 10 just by the merit of their weapons capabilities, as opposed to any particular writing skill or originality of attack. Also, the range of terrain which favours a gunman is absolutely huge. Pretty much any area with line of sight longer than five meters the gun reigns supreme, until you get past its barrel it will kill you at any range up to 300 feet.
The compromise in my opinion that could potentially balance things in a tournament setting is by making guns a significant tier increaser, setting even a completely ordinary human at the level of a T2 or T3 character on the old system, ensuring that their body at least is fallible to offset the inherent power of a gun. For example, if you gave the Clockwork Man of mine an automatic weapon, he would be damn near unbeatable for anyone save those of a significant higher tier than him, due to his equally powerful physical characteristics.
Just an idea, I'm going to go get drunk, later.