Are their any situations, other then switch shooting, with these guns where the primary attack is better then the charge?
Use of Callahan / Tundrus / Alchemer's normal attack?
Your target may move at the last moment. You may be better off firing several regular shots - some of them hitting their target - than charging and firing one big shot and risking a miss. Your choice.
The regular attack of the Callahan is perfect for pinning down Devilites (even overtimers). Even better for switch shooting Callahan/Blitz (or Plague) since the Callahan flinch is strong enough to pin them for a good Blitz spray.
I'm guessing the same could be done for gremlins with the Grave and Repeater (working on getting those to test).
Magnus line normal attacks have a very high interrupt potential on any monster. Normal attacks without switching often lock the enemy in a constant flinch.
I will also add they finish off enemies the charges don't completely obliterate
Are you asking about raw damage per second? That would require some clarification (are you shooting full clips or what?), some data (maybe not yet updated since the gunner update), and some simple calculations.
Of course, regular attacks take less time. So they help you interrupt a monster repeatedly (e.g. gremlin mender). And they let you shield more often, which might help your defense. But that's not what you were getting at?