If you want Kira’s HP and speed with shotguns or SMGs, you want Proxy. Proxy is not Kira.
Kira has her own set of strengths. Dreiss can be vicious at long range, but the combination of a battle rifle and high mobility works remarkably well on its own. Kira provides fire support, and she does it well, from any angle. You’re not meant to be in peoples’ faces with your weapons, but rather use your mobility to outmaneuver your opponents at range, and to flank your opponents.
Playing Kira well requires mobility and flexibility. Kira’s ability just doesn’t work if you yourself are up close. What you want - in my experience - is to use your laser and your rifle together. Get a laser close to your enemy, and force them to run, then shoot them. Or force to to take cover, and finish them with the laser. Quickly swapping between laser and rifle are essential.
EDIT: By the same token, Kira isn’t the merc you want to hunker down with. If you camp a window and expect to win with Kira, you’re doing it wrong.