Sven is right re the way internal tyranny inside IBDD would work (at least that's the prediction) - should lead to internal progress away from tyranny.
In terms of Dan Carlin's idea: I haven't read his work, so I am not sure if this is accurate, but I suspect he does not take into account the selectorate theory of politics (or fallibilism). Selectorate theory is (in principle) what's laid out in Rules for Rulers. The problem is that corruption is a tool in a democracy, and this changes the dynamics for both the candidate and the voter. Carlin's candidate (like a Flux candidate) might be elected if most voters were swing voters, but because we can't use corruption as a tool we're naturally at a disadvantage. (Proportional Representative legislatures offers more opportunity, though, since we need fewer people to get started).
Under IBDD a successful candidate is a universal resource to compete with such corruption (the kind used to keep MPs in power) and help produce good policy simultaneously, however, Carlin's candidate needs to have a correct theory of politics, first (which I do not think most current political commentators have), and only if they're right can they actually make change for the better.
I have a lot of thoughts about exactly why I have this point of view, but they're a bit excessive to type out here in full.
The problem of 'what is the theory of politics to choose' is a difficult one, and AFAIK IBDD is the only system that claims a) not to be perfect and b) to enable a transition to a better system of politics more easily than what came before it. So IBDD is not an end point, it's a starting point. It's not designed to solve every problem, it's designed to provide the necessary conditions for progress in a somewhat optimised form. Now I think Carlin has the same goal, but makes the mistake of presupposing some solution that is somehow not theory laden, which is impossible. If he acknowledges a specific theory that might be wrong, what do we do if it is? These representatives could spend years fighting for change and actually not solve the problem they intend to! Every conclusion, every policy, every decision is theory laden, and without exploring the underlying explanation we don't know if what we're doing is going to be a mistake or not, so his suggestion doesn't get us anywhere directly, it still needs some extra creative juice - and that is what I think IBDD is.
Well, that was longer than I intended.
Re: the US stuff and your earlier post, will set a reminder to get back to that tomorrow.