I've played a few vegans, the thing to keep in mind is that it's best to be as hypocritical as possible. You only trigger penalties by killing animals with melee, so just murder them with spells, summons or ranged attacks. If you don't you'll lose out on a lot of XP. Besides...they'd breed too much and starve! Thin out their numbers! So far my combos have been Vegan/Sniper/Big Game Hunter (he hates animals so much he refuses to eat them...and kills only for sport!) and a Vegan/Vampire (yes, somehow this works). The animal swarms seem to really only be a big issue right now at level 1, since that has the densest animal population (diggles, sickly diggles and batties, with only the blobbies and gnomes otherwise).