When you are frozen and click class ability to break out, you will activate the health regen but not consume the dodge so you leave the freeze with more health and have a dodge up to get away. If you dodge immediately you wont get a second health burst but if you wait a second (even shorter than the attached gif) you will get the health back. This works for any ability that procs off of class ability but not ones that change the class ability like the new hunter helm.