"Worst Optimized" isn't a term you can just throw around. Unless you've seen the source code and know everything about the work it's doing, it's simply not a judgement that can be made. An application can be perfectly optimized, running at the theoretical maximum possible speed, and still bog down a computer. Slow != poor optimization.
Considering the Optimisations we managed to the 1.04 patch (currently in public beta) there is probably a case to be made that HoI3 could of done with more optimisation at release. Worst optimised it may not be, but we could of done better on that department.