This. Until we see Slade do more than kick around some fodder Merlyn puts an arrow in his head before he gets near him. In theory Slade should win but we have no feats and we saw Ollie take down Cyrus who has the same stats as Slade and Merlyn was stomping Ollie quite convincingly.
He doesn't really face alot of character with telepathic powers besides with the opposite power of him aka light powers .
The Darkness's armor cannot be penetrated by psychic attacks as shown in The Darkness #14 then elaborated on in The Darkness #39. I'd post scans but I don't have access to them but those are the issues where its shown telepathy is basically useless against him.