I think Caspar is a 3/10. Struggling to get onto a mount, and having a lack of good ranged options (other than a training bow/iron bow) hurt him in the late game, while his low bases put him in a difficult spot in the early game. If I'm recruiting units from other classes in CF/SS he's the first one to get demoted to adjunct.
That doesn't mean he's without his uses though, Killer Gauntlets War Master is a great way to take a bar from a demonic beast, and I even remember once giving him a full Steel Axe+ to OHKO the Death Knight with Exhaustive Strike in his paralogue (on SS of course).
I don't think he's the worst unit in the game, but if 5 is average he's well beneath that.