I think battle magic is the way to go, but it's spells are so hit and miss you generally need a lore familiar anyway. It's such a shame beyond...
I see no reason to put 20 points on a champion, with just a single wound, low initiative and one unlikely to charge. I'd take spears for the unit...
Same answer for a different reason. Most hits seem to come from impact and stomp. So I'd prefer the st6.
Don't take a champion for your Kroxigor. You risk getting into combat with something big and being issued a challenge. You three options...