Chaos damage is completely useless. Lets assume you go after a lava elemental with 100% chaos damage. The resists of a lava elemental are 62/23/20/100/44.
First hit is randomly cold, it does good damage Second hit is poison, it does NO damage at all. Third hit is physical, it does crappy damage. The thing is, you want predictability in your damage. Most elementals have a moderate dislike to cold damage, with the exception of Ice and snow elementals. Two of the elementals are completely immune to poison damage. Chaos damage will roll poison theoretically 20% of the time, whereas cold damage will never do 0 damage. Most warrior types are bound to have chivalry on their template, so go cold damage and elemental slayer for elementals, and use consecrate weapon for ice and snow varieties. If you're really serious about being a warrior, and pvm in general, you should have a good idea of many commonly seen monsters in the area you intend to hunt, and bring the appropriate elemental weaponry.