When coming up with the voice for Sirol, the Andorian security officer of the USS Mariner (watch here:
http://vimeo.com/28040680 and check out my YouTube channel for some of my other work:
http://youtube.com/dlz2000 ), I threw in a bit of Odo, a bit of Word, and a bit of Martok. I pictured him a bit more square-jawed. I have yet to do a voice like that in a way that's good for the vocal cords, but I did it. I'd say, if you can't "relax the vocal cords," then at least make sure they're lubricated some how. Potato chips are actually pretty good for that.
But, it's not just that the voice is gravelly and gruff. Think about the character too. Watch his episodes and read about him as a person and try to feel what he feels in a moment of schadenfreude at something Quark has done. Try to empathize with his quest to understand his changeling nature. Try to understand his unrequited love for Kira.
Such an understanding will be far more helpful in constructing the voice than simply being gruff. Voice acting is more about the acting than the voice.
The voice you did isn't bad, but it's probably better suited for a Klingon.