There is actually a way to keep those optional paths in a dungeon and not give it a path of least resistence.

Randomize what the actual goal is for each dungeon.

One time its the mini-boss or two on one branch... one time its a mass spam of mobs three times in a row... one time its getting 4 crystals in random parts of the dungeon to unlock to the door to the final boss.

So they can actually make optional or branching paths but make which one you need random or a combination of the above.

This would in essence never make it the same dungeon twice.