Frostbringer + WESS makes a good combo until you can replace Frostbringer with Infestation.
As an interim solution before getting Infestation, WESS +
Trochilic's Skean (procs at 46) would actually be higher hate from procs, but Frostbringer would be higher DPS.
Infestation + WESS would be the highest threat generation outside of epic/VP/ToV.