I take Starcraft here as example - what if you make the squares gradually grey out?
Gun Turret @ 399/400 Health
Current implementation:

Suggestion:

Of course, if the turret is at 350/400 then the square should be completely grey, as in the first picture. But at 399/400 it should be just slightly darker and gradually get closer to the grey color as the health decreases.
Also - just as a question, what about health bars like the player one for other units (one without squares)? The squares don't seem to be related to a certain number (e.g. they are each 50 health on gun turrets, but 10 health on belts).
This is by no means a huge deal, but I would love to see this optimized, especially since this shouldn't take longer than a few minutes to implement and it would make reading them a lot easier.
Edit: What about giving an option to turn health bars for enemies on all the time? I for one have trouble seeing enemies at certain moments until they take damage, due to the lack of health bars.