Kinda a DH newb but I have played alot of HoI2 and a little bit of AoD. Anyway stuff in DH takes alot longer to build in alot of cases. This results in smaller armies thanwhat one is used to in HoI2. THis however also hurts the AI alot.
Maries seem a little pointless. It seems every game I play Germany does not have enough divisions to secure every beach in France. THis makes a D-day in 42/43 very easy. Once you break through is is stupidly easy to rampage through Germany. The few German units seem to likedefending the neitherlands regions and Cologne area. THe South is usually wide open. I used a single motorised infantry division to drive right though, annex Slovakia and Hungary as the USA. A similar thing happend in a british game. By 1943 I was pushing deep into the Ukraine.
In the pacific its even funnier. As the British the Japanese never attacked the Raj and barely got indonesia. In my USA game a single 1931 marine unit captured Truk, Iwo Jima, Okinawa and most of the pacific. The Japanese invaded the phillipines with a singe inf divisiosn that was actually from Manchukuo. I built some more marines but they were not really needed although the AI had a hard on for recapturing Saipan.
The AI has always been bad in HoT2 and varients but at least in the original game and in AoD you actually need units. DH has less micromanagement I suppose but has other issues such as stupidly long build times for fleets. You won't be building replacements anytiome soon if you lose a CV or something. 6-12 modern CVs more or less wins you the game anyway.