If my two cents is worth anything these days what with the economy being the way it is, my major nitpick would be to make that MUCH shorter. If I was at a con and I stopped by your table to find out what your comic was about, and you hit me with that, I would more than likely lose interest by the middle of the third sentence. It has nothing to do with the content of your comic, mind you, it has to do with grabbing the attention of the person you are talking to. What I've found the trick to be is to hook them with a very short elevator pitch, or "blurb" if you want, and if the person wants more info THEN you can step up the game and go longer with it.
Here's what I would do with your comic (I'm not familiar with the comic itself, I'm just working off of the elevator pitch you gave):
"An aging vigilante near the end of his career and his possibly immortal, super powered cat face the very real specter of retirement, incarceration or death. For the first time in his life Artur is experiencing more trouble than he can handle and he may not be young enough to pick up the pieces and start again."
All that is is just the first and last sentences that you gave. Forget about giving too much detail about the character or the story; you want the potential reader to discover all that on his or her own. Give them the essence of the story, and, if you can, a little bit of an eyebrow raiser (your "possibly immortal, super powered cat" line or my "demon that bakes cookies" line). I'm willing to bet you can get that pitch even shorter and more intriguing if you tried.
It comes down to something I was taught very early on in my writing career and again later when I was in advertising: K.I.S.S., or "Keep It Simple, Sally!"