I dunno if you know this AS, but I've noticed through the years that you like to use lot's of reflection (and not forgetting rust obviously) in your renders.

Nothing wrong with that, but did you know that the more reflective your materials are, the less colour bleed you will get?  I say this because you're after that colour bleed, and because you're following the rules you're kinda making it harder on yourself because the more reflective your material is, the less Ambience/Diffuse is allowed.

Remember, less Ambience = less colour bleed.

As for the HDRI tests, lol, I dare not even get into mixing things with it yet.  But yes, I say you're right to suspect the amount of light sources for the overpowering effect.  Kinda like using lightdomes where eveything feels oversensitive.

Anyway, I would test HDRI using only fully Ambient/Diffuse materials, at least that way you get to see the optimum results possible with maxed-out Ambience.