If a healer casts regen on you before you pull... You smack them firmly on the nose, shout "BAD HEALER!! BAD!! NO!!" and you right click the buff to get rid of it..

If they learn quick, give them a treat by a light swat on the butt saying "good girl/boy!"

If they continue to disobey you, you rub their nose in it by waiting for their regen, running into the largest pack of mobs you can find (multiple packs are good) and then running back to them and dancing, or sitting, /pose is also acceptable.