Well, Grievous Does seem to be quite a bit more powerful in all EU series, one way or another, and definitely more "honorable" when it comes to granting a warrior's death if possable.
Don't get me wrong he is smart enough to retreat if outgunned as he should be.
I mean, I do think the last Obi/Grevi fight makes Grevi look more like a cocky bastrd than a serious honorable fighter. He should have tried to just finish Obi off rather than toying with him a bit, as we know he can snap his neck quite easily.
While I have no problem with him using his Magnaguards in the fight, considering that he might be wounded/weakened, there is no excuse for dumbness in fights, consider him being a true warrior as stated.