In Street Frighter X TEKKEN, Kuro, Toro and Cole are not playable in arcade mode and I have yet to heard a clear reason why.
One explanaition I heard is they are not in arcade mode because they are exclusive to the PS 3 version, but Kratos is exclusive to the PS 3 version of Mortal Kombat and he is playable in all modes. I've played as Kratos in MK and I've fought against him when I played as other characters (he can resist Sub-Zero's ice ball BTW). So why not have Kuro and the others playble in SF X TEKKEN's arcade mode?
Mod Edit: Added label. Want to learn more about labels? Click here! -Super_Nova2k13