Well, it meets the criteria for an Artifact, judging by UESPs definition. Unique appearance and effect, so I'll consider it as such. And of course, I am very happy with the Imperial Insignia on it. Feels right, considering who wielded it

I definitely think it is an artifact, too. Not on the same level as the many Aedric, Daedric and other such artifacts we've encountered, but still. It's not mundane, it has a story, a history. Wielded by a General of the Imperial Legion who, even in undeath and corrupted by foul magics, was staunchly loyal to the Empire he served whilst still living.
There's every likely hood that we'll never see the Champion's Cudgel ever again, but it is still an artifact, albeit a minor one.