Recently, however, I've started playing a marauder so I can experience the other side of the story. And as I'm leveling up and doing all the quests, I keep thinking, "How can anyone take the empire seriously?"
Playing as a Light-sided Sith Warrior
you can see how the Empire took over half the Galaxy.
Playing as a Dark-sided Sith Warrior
you do begin to wonder how anyone in the Empire can survive to be old enough to breed.
I think the problem is their "Dark-side" is more "Raaaagh kill!!!!111" than a Darth Sidious or Darth Vader calculated self-interest (they might blow up a planet, but they do it for a specific goal not just for "fun").
However it's arguably worse as a DS Jedi, because that just comes across like a sulking 3 year old much of the time.