Think of it less like throwing a Balrog or a Kaiju into the midst of a bunch of mooks, and more like a Warg Rider. Yeah, it'll give you an advantage, but it's hardly unbeatable. His advantage is more that, like Mystic when she has her powers, he's incredibly hard to put down and keep down.
Plus, if Boris is made incredibly easy to defeat...what sort of chance does Bridal Shores actually have? I mean, if this force can go straight through a full grown, specially raised Massacre Wurm like it's nothing, what exactly are the royal troops going to do to this force? Other than die like flies.
Will post tomorrow. Had way too many distractions, and am way too burnt out tonight.