one trick for your mages is if they cast invis right before the tear gas goes off and they go full invis they can avoid the stun and add alittle bit of dps to the boss or any remaining adds up. It works because I do it all the time on my mage but the timing must be precise or you will waste it and still be stuned. Rogues may be able to to the same thing with one of their vanishing moves but Im not really sure if it works.
Indeed, rogues can vanish and accomplish the same thing. This is particularly helpful if you happen to get an add up during the transition the mage or rogue can almost solo kill it during the time period where everybody else is frozen and Putricide is RPing.