Once you enter the battlefield, go to the lower right corner of the map as quickly as possible. You will fight the 3 bosses this way one by one instead of taking all 3 at once.
Have the Tanker lure 1 of the MVPs slowly until it goes to where the attackers are positioned (which is at the lower right corner). Attack until it dies. Buff and heal before luring another one and repeat until the last MVP is defeated.