User blog comment:Omega natsu2/Episode 179: Gray vs. Rufus, Review./@comment-3424593-20140426035938/@comment-7418318-20140426093953

He can be the most flexible mage, yes... but if his magic-power pool isn't up to snuff, that would still leave him far from the strongest.

Also he severely lacks in resilience and if you either get into close enough range or have spells with almost instant effect (like some of Gildarts spells for example), he's toast.

The episode showed it very clearly in Gray's final attack. He was so close that Rufus couldn't put up a defense in time to block or otherwise avoid the attack.

Against someone like Jet, Racer, Mirajane, Erza and Bacchus Rufus would have a pretty hard time I think, unless he can immobilize them before they get so close that he can't react in time to their attacks.