Malzahars Ult

Does anyone know how his new ult works? Like I get that it has his old W attached but is he getting the percent health from the W and his Ults damage? I feel like if this is the case its super overpowered (not that I'm to upset about that because I love malzahar) but if it only gets damage from the W percent health then at the same time it does no damage to squishies or tanks a like. I feel like if this is the case he can't kill tanks or burst squishies anymore. Does anyone know?