Loosing 10% spell suppression when casting exanguinate(life)

The title can't be more clear , unless i missed something in the patchs in witch case am sorry but this seems a bit weird .

Whenever i cast exanguinate that cost me life i lose 10% spell suppression , i go from 28 to 18 any time i cast it dunno if it's normal or something related to spells that cost life .

Revenge of the hunted only gives you 10% spell suppression on full life so that might be the broblem

Thanks mate :) that's it , i never saw that spell suppresion line in the notable .