Well I use that very set with thunder punch as my coverage option to be specific.I still find CharX to be superior to Mgross. For typing and sheer destructive power, accept no substitutes.
Main difference is that Mgross can run a fully offensive set where charX basically has to run a support move. Agility builds aren't even that common anymore, are they?
And yep not getting burned and the ability to have flexible ev spreads really make char X a great pole position mega, however in a team that doesn't rely to much on volturners I found bulky agility Megagross to do wonders.
And yes I'm amazed at the amount of empoleon on the ladder at the moment.