Gastrodon is not really common, though Grass Knot is useful for catching Water-types on switch, but is not sufficient to leave a dent on most of them... I think that Infernape works better nowadays in sun teams. I've used a Choice Band set on a sun team, and it's wallbreaking capabilities are just monstrous. Believe me or not, I've used the MixNape set on a sand team, it was there just because I had to use it to cover what my team couldn't destroy otherwise, my team was different at this time. But it was capable of leaving holes on the opponent's Pokémon, to leave the rest of work to Landors and Tyranitar. The sandstorm damage is not much of a nuisance since Infernape cannot take a hit anyway. The best way to use Infernape nowadays is as a wallbreaker. A trivial comment: normally I hate to use Overheat since the sp.atk drop forces me to switch and there are situations that I would wish to have Fire Blast instead. However, Overheat has amazing synergy with U-Turn and MixNape still has it's other moves, Close Combat and Stone Edge/Mach Punch.