I personally dont have a second yet I cant seem to decide which characters to co-main, I really like raiden but I cant seem to be effective with the character. I play lao only and if it weren't for casuals I wouldn't bother trying to learn a second.
the raiden vs cage is a weird one and I think there is a lot of unexplored stuff in the matchup. if you go raiden vs cage in tourney you dont have to worry about people counterpicking you or whatever because that matchup is supposed to be in cage favor.
and yes cage is frustrating, very underrated as only 4 characters beat him and he destroys the rest of the cast