One of the most far off is actually Peter Dinklage. He's far too handsome and charismatic to play Tyrion. Supposed to be ugly and gross in manner.
He may be supposed to be ugly - but, really, it can be argued that him being a dwarf is enough to be considered ugly; it's not like anyone mocks him or thinks of him mainly as a guy with an ugly face, they call the Imp because he's a dwarf. Being ugly wouldn't make him a freak anyway, I'm sure they have lots of ugly guys, being a dwarf is his main characteristic.
However, I don't know where you're getting the "gross in manner" thing. I'm 200 pages in and Tyrion is really smart, funny and charming, and one of the least gross-behaved people in the book. (And the book sure has its fair share of gross people, starting at the top with the shithead prince and his mom and the even shittier wannabe king.) Isn't he supposed to be someone who has the mind and other non-physical qualities as a contrast to his appearance?