I'd like to add that a 104 HP / 232 Sp. Atk / 172 Spd Ev spread could be recommended, since it let's you outspeed and OHKO offensive Torterra, as well as anything that aims to outspeed Torterra's odd base speed. It loses only 5 Sp. Atk and 7 Sp. Def, the latter of which is mostly 'filler' anyway. Further up the speed tier list, we find max speed Aggron, Max speed Gorebyss, and Max speed Omastar. The latter two are rare, and most likely outspeeding you in rain anyway, but OHKO Aggron with an unboosted Surf is tempting. This forces you to run only 204 Sp. Atk Ev's though (and 200 Spd).