I thought Garchomp's primary reason for being banned to Ubers is having the stats of a Pseudo-legendary coupled with perfectly balanced STABs. The Dragon/Earth combo is resisted by only 2 Pokemon that I can think of (Skarmory and Bronzong [pre-evolution doesn't count]), and Garchomp has a huge attack stat, decent speed, and the 150% boost for same type to both of those moves. Even without the extra evasion from Sand Veil, he is just too powerful for standard.