Yeah. To me the reason I can tolerate Jar-Jar more easily than Grievous is because Jar-Jar is supposed to be comedically stupid, therefore I can see past his antics. But Grievous is supposed to be a villain, and not some hapless henchman like the Nemoidians, but, like you say, a badass. He's supposed to control the droid army and is talked about like some fearsome monster.
...But he's not!
Just when I thought he might finally be cool when he starts fighting Obi-Wan, he becomes more idiotic still. His whole four lightsaber plan, while cool in concept, was just useless. Then he transforms into quadraped mode, which is ridiculous, and spends the rest of his time driving away inside of a giant tire... that also becomes a quadraped. What is with Grievous and four-leggedness anyway?
And then, mercifully, he dies. And his death scene is actually not that bad. Well, at least he has that one saving grace.