Mana siphon has to be nerfed

It is inconcievable for me, what kind of a brainstorming session it was, that the current iteration of mana siphon was conceived.
How is it possible that nobody pointed out how massively idiotic it is?
I just fought the savannah map boss and it had mana siphon, literally blink of an eye and my 5890 mana was gone, WHY THE HELL MUST THE MANA SIPHON RATE BE SO GODDAMN FAST!?
The mana siphon aoe just barely touched me and all my mana was sipped, it felt like it was a tenth of a second that it took for it to gargle all my mana away.

Sounds like Mana Siphon uses the same mechanics as mana % steal for players. Only problem is, bosses have mana leech defence stat and players don't.

Pretty sure this will be balanced as neither mechanic is working right now