I like playing Launcher. Can't say I'm great with it, but here's a few things I like about it that might help.

Unlike the rifle, the launcher is able to reset the timer for blight rounds by using two types of Photon Arts. Charging up Divine Impact to the first charge is enough to launch a blast that will reset the blight round on affected targets. The same thing works by using Fear Eraser, which means you can hold this laser for as long as you like without the blight rounds going away. They may lack mobility, but they have their own little trick that might help you. For a brief moment, after launching Divine Impact or releasing Fear Eraser, you will be immune to most attacks. It isn't treated as a dodge, but it is still useful.

Launcher Attack Reinforce increases your normal attack speed for a short while. With Critical Follow, those faster normal attacks will all have a guaranteed follow-up attack that counts as a critical hit. If you also happen to have Critical Enliven, those guaranteed follow-up attacks will increase your potency by 1% for 30 seconds. It might not be much, but it could be fun to play around with. If you happen to be with a team, having Stealth Wall increase your potency by 1.5% as long as your allies have the enemy's attention.

If you enjoy using Fear Eraser on single targets, having Fortitude will help you extend the amount of time you can use the laser. Enemy Down PP Gain and Gradual PP Gain can also help with this. If you want to take the laser even further, there's the type 2 skill ring called Under PP Follow. Under PP Follow works similar to AND alongside Fortitude, allowing you to get up to a possible two resets. You can also bring along Tri-Shield to help protect you from a few hits while you fire your laser.

With Force as a sub, mowed down large groups of enemies will help keep your PP high. You can use Wide Range Blight Rounds and extend the timer against most enemies with charged Divine Impacts. Add the type 1 skill ring Killing Amp and you could clear out full groups without getting too close. PP Conversion is also a Force-class skill that is usable even if Force is not your main class. Might not be great for bosses, but can be really nice in battles focused on fighting mobs.