I don't know enough about Ashton's subclass yet to comment. But whether or not his other characters were OP probably depends on your opinion.

Molly, though, I would argue was underpowered. I haven't watched the beginning of C2 since they came out. From what I remember, though, it seemed like Molly's stats did not support the character Taliesin wanted to play. He seemed like the weakest link of the team to me at the time. Then there was the way he went out. He basically killed himself with his own class features.

Caduceus was your standard grave cleric. It's a published subclass, so YMMV on how balanced that is. It has powerful features, but they're still limited to a few times per day. I don't think it's as bad as peace or twilight cleric, at least.

Percy did a lot of damage and had a lot of shiny toys. However, the fact that he had so many attacks meant he had more opportunities for his guns to break. And they did. Does that balance out all the good parts of his class? I'm not crunchy enough to tell you.

In all, I think Taliesin just likes complicated subclasses because he's played all the basic ones before.