The draught was a super neccesary addition for AQ40 as none of the mobs had any typing, nerfing both rogue and hunter going into the raid.
This problem will repeat itself going into Naxx. Faerlina and Maexxna are the only humanoid/beast mobs in the instance, which will cause these classes to have outlier performances against these bosses. In the interest of balance, I highly recommend adding another Draught for undead mobs for a more uniform performance against the bosses in Naxx, and to prevent players of these classes from feeling nerfed going into the undead bosses