You make some valid points. Soran was definitely not a soldier. He was a pretty poor shot with that disruptor thing of his. Even if that's the only hand weapon in the history of Trek with visible destructive power. With the dampening field, I suppose it is possible the Klingons just scooped up everyone in a given area. They did ask Soran for coordinates.
Still, that doesn't explain why Soran's torturing Geordi for information he already has. Unless Soran just gets off on torturing people, but that seems out of character. "There was a time when I wouldn't hurt a fly" going to casually letting people die still don't translate to sadism. It's possible, Soran just made that goof like you said not thinking things through on a military level, but I don't think the writers were that far ahead and it's just a coincidence.
Soran really could have been an interesting villain if things were written better. But the whole Nexus plot is just doomed to not make sense.