SMG? They seem to be like that. Low defense front liners. You definitely need a fast growth rate on them to use one at the start. Sayaka Ushijima (high damage, ok defense, high hit) or Mina Makabe (sp? More evasion than most HGs at low levels) but not sure where she comes from.
Is there someone that they pair best with? ie: those with a similar range? I guess the game wants you to tinker around with stuff..curious how she'd be alongside 5 HG girls.. Not that that would ever come in handy. (Or would it? I'm still learning. Definitely get the best results on 3x AR, SR)
I don't know how the enemies choose targets, but I would think pairing SMGs with other front liners who can take hits before them is the way to go.