Sad that nothing has been done to address this. We do learn to adapt though even without being able to see the red circles:

Fungal Grotto I - Kra'gh the Dreugh king - Cannot see the red circle due to the grass, have to watch for the animation.
Ruins of Mazzatun - Zatzu the Spine-Breaker - Cannot see the red circle due to the grass, animation is well choreographed.
Cradle of Shadows - Velidreth - Specifically in hard mode, once the Attronachs with the torches come out the red circles become non existent within the light. Easiest way to avoid them without seeing them is to watch the arc from the statue, listen to the sound queue and roll away from everyone.

I'm sure there are a plethora of situations where the visibility of red circles can be called into question. An easy solution would be to change the colour of the AOE circles themselves. API colour management would be excellent as well as you have stated, if the development team does not want to go ahead with a graphical mode for the various types of colour blindness.

Hopefully this will be implemented someday....