Haha well some of those are spells you mention are chaos/nature and to get champion level you kindo need to take full life magic and warlord 

Trying to pick up extra spell books depends on the RNG gods in control of those nodes. But seriously those longbowmen are insane. 2 volleys at most will take down Great Drakes, Great Wyrms etc. 

Shrug if you play on...impossible? setting most nodes have spell books. I found that that high of a level bowmen, even elven are useless. Granted I just play dark elves because they're the best race. Shrug.