It is possible to discover an enemies HP value if you have damage numbers and combat log active. Fighting through the fusions i realized my last hit damage is dramatically smaller compared to the other hits. Then I began to add up the damage to get a number and tested it out on the same enemies to see if i get consistent results. That was when I noticed that it stayed exactly the same. If HP values are irrelevant then you change the template but otherwise I think it might be interesting to keep track of.