It seems Alraune's charm effect bypasses Heart of Stone's effect which clearly states that charms inflicted on you or your own charm have no effects. I learnt it the hard way.
You can be inflicted with Charm, but it will do nothing.
While that'd make sense, I still dealt reduced damage to Alraune, and took a bunch of attacks from my teammate doing Lead Storm on Alraune as I jumped to protect the plant. So I can clearly say that the charm still effects me.
The issue where it didn't negate the charm damage substituting effect has been corrected. Damage reduction should be working fine but I made a secondary adjustment for that as well.