You can use the Master Crown immediately as he comes in for the Staffs. That instantly makes him better than most fighters, even if you can dispute the usefulness.
The fact that you can use the Wyrmslayers and shit for those enemies is irrelevant; the fact of the matter is that he can still do it from base level, and I do believe that something like Elthunder is cheaper than a Wyrmslayer, and less fought over for than Beastfoe (which doesn't even affect Dragons btw).
Where did I say it was reliable? I said it wasn't bad, I didn't comment on its reliability. The fact is that he can roughly dodge shots in terrain, which there is a bunch of in this very chapter. And so? Warriors are bound to have something like 30-40% hit on him, so they don't hit him very often either. It translates to close to around 70-80% real, which is still pretty decent. Once again, I didn't even say it was reliable; I said it was decent.Also, coming into Tibarn's maps without requiring a slot = win, especially since he's forced on you in 4-2.
Low in level hurts his case, but only slightly considering he comes at least L10 anyway so he can use a Master Crown.