Exploit 1:
Gunship Battle (works with heroic also): You can use distract on the mage while he is running from the spawn point to the place where he casts Below Zero and get some free time to dps him before he disables the cannons and also delay the spawning of the next mage.
Exploit 2:
Professor Putricide (normal mode only): If you use Vanish while Professor is casting Tear Gas you will not get the 10 second stuns and can continue doing damage to the slimes/boss. Might work with mage invisibility as well.
I have searched for these but haven't found them anywhere. Delete them if it's a repost.