Apart from that, i think his Hero turning power is misplaced. It wasn't him but Saruman that put the charm on Theoden. The only thing he did was being a spy of Orthanc. He should have some other high end power, and Saruman should have his old power instead.
Totally agreed. It was always Saruman who had the power of persuasion and corruption. Grima was always a weird choice for a hero, never really sat well with me. But if he is to stay, then an appropriate high level power should be either a less powerful version of Saruman's ability to convert units (temporary effect, as opposed to Saruman who should have permanent effect on normal units) or some kind of truesight power, reflecting his ability to predict the reasonable course of actions of his enemies as seen when telling Saruman what Theoden would most likely do (ie. retreat to Helm's Deep).
