I'll use my runs through the personal story to give the best answer I can
Basically, the power of the PC varies, but even then they're still quite a powerhouse, using for example Vyacheslav
While the order of whispers representative could've just sneaked around doing her thing, without the PC, Vyacheslav would probably fire his weapon anyway, and both her and Eir would be overwhelmed with Icebrood, not to mention the destruction of the Priory main outpost
While on the other hand, some of the commander's actions would simply not be possoble if they were all alone, for instance in "Victory or Death", before storming to Arah, you need to gather core pieces for the ship, and to do so you must go through champions, which the commander definitely wouldn't be able to take alone.
TL;DR
The Commander is powerful enough to turn a hopeless situation into a victory, but not so powerful to the point of doing that all by itself
But that's how I see it, not an absolute