Is assaulting Bunkers too hard ?

[Gregor]

That might be the case but clearly not because strongpoints get overrun to fast. Its more likely the AI not mounting a clever defense or a too static one. As all my test have show, fortifications with only small units inside last unrealistic long against assaults undertaken by overwhelming forces (10 against 180). This issue has already been discussed with the Kursk game and i feel its still there and needs a better balancing.

I have to disagree here. A competent attacker seems to have a faster progress in the game both in Normandy and Kursk than in RL if playing a competent defender more often than the opposite. Especially is that seems true for the "bunker" scenarios, except possibly where severe lack of AT weapons making it difficult.
My view on this is more that you wouldn't be able to get all those 180 engineers into position in an attack against a fortified area against non disrupted/suppressed enemy. As the defenses are represented by fortified hexes and not my solid lines this is working as intended and as long as the bunkers are not disrupted they will hold the enemy of.

At DDay, whole WN's (Wiederstandsnester -> Fortification hexes) surrendered with 21 men left (out of 40 or 50). In most WW2 combat nobody fought to the death. Units usually fought as long as they could keep a sufficient amount of cohesion and had contact to other units and their superiors. A surrounded fortification hex with only 8 combat ready soldiers left that gets attacked by 180 combat engineers should in majority be taken by the attackers and not (in majority) fight of the assaults.

I do agree that they usually didn't fight to death, at least the Osttruppen, but I suspect most of those 21 men in this case would be represented in game as casualties, and in addition the unit disrupted. But again, that abstraction works for me and I don't feel the advance is too slow in the beach scenarios, but I do understand that you and some others feel it differently.

Would be fun to see other approaches to those scenarios. One approach could be a solid line or impassable terrain between the bunkers alongside bunkers with static troops with a facing. But I suspect both those approaches would result in other problems occurring...