Maybe the problem with his depiction of Ronon was just that he was not good at acting as the stoic "boring" character. Which we have seen can be done well. Teal'c is a fan favorite, as well as Seven of Nine from Star Trek. Both of those characters are intentionally written to be very bland, but the actors were able to act with a performance that people were able to enjoy. Ronon was also written to be a similar stoic warrior type, but unlike those other two examples, his performance just came off flat. I wonder if maybe a character who is intentionally written with more dynamic range and everything is just a better fit for his acting abilities. A stoic warrior is just a difficult act to pull off.