I wouldn't say it's a bug, it's probably just a design flaw. Maybe the devs thought that if you hit with a fire spell, a character with retribution would "splash the fire back", and since that creature heals with fire, it'd heal by hitting you. It makes sense, but on the mechanical level, it makes the build unfeasible (at least on a solo gameplay), specially because it's not something you can deactivate: it means you're spending combat points that actually work in favor of your enemy.
That is exactly my point.
I am fine saying in some circumstances that spec has no effect, ... Fine but not if it works against you.
Especially since you have no way to turn it off nor any counter (assuming decaying touch doesn't affect this).
Now about the definition between design flaw and bug we could go on about it but I understand what you mean and agree to a certain extent (Isn't a design flaw a bug in the design? etc.)
