It's actually 0.1% per +1 hate added. So for example if you hit a mob for 500 damage and you have +24 hate socketed you will generate 500 base damage + 2.4% additional enmity or an extra 12 for a total of 512 enmity. With heavy darklight should be able to get close to +200 enmity with a double socketed weapon and belt. Without heavy darklight, still pretty doable to do +50ish hate on just main hand and belt. An extra 5% is nothing to sneeze at in a party full of min/maxers who are outputting insane damage.