[Edi]

Making an Onmyo-ji with a nature random a prophet for Jomon results in a scary, scary combat mage.

Reason? The H1N1 holy spell Teaching Sign increases the caster's magic paths by one for the duration of the battle, so a F1S2N1H3 Onmyo-ji casts teaching sign and is suddenly F2S3N2H4 and so forth. The Meditation Sign (HW) halves current fatigue.

Dai Tengu is also scary, because they have a fixed nature pick. Teaching Sign turns them to A4E2N2H3 and then you can crank up reinvigoration with Earthpower and then start spamming Thunderstrike. Pick a bunch of them, give one Staff of Storms and it's Teaching Sign, Storm Power and that's thunderstrikes at A5 and they'll keep going all day...

I'm quite certain that some of these things will make for pretty significant changes to combat effectiveness indeed.