This battle's practically running on a script, which Ardon wrote, and he wrote that script all the way through to a victorious end. He might be uncertain about his party's ability to pull it off, but he's in the best position of anyone to know the odds and he's very confident in his own planning ability. I really doubt Ardon will actually be surprised by them winning, and he's realized that sticking together gives him the best protection he's likely to find.
Ardon might be hiding out to prevent any possibility of confusing him with his impostor, but I expect he'll be on hand to claim credit for the victory (with actually pretty good justification) the moment he thinks it's safe. He might even crash the battle, having just waited to be sure his support is all there first.
You don't think Ardon is the 'imposter'?
The Giant There are no mistakes, because there are no rules. NONE. No, not even that one.