I think Warhammer is a step in the right direction for Total War, however some game design points leave me somewhat dubious. The Chaos Invasion is just a reskinned Realm Divide/Civil War, and I don't think Creative Assembly have got this mechanic right yet.
My main gripe is that it's so artificial and predictable. By this I mean you know when, where and how Chaos are going to invade. Nothing you do throughout the game affects the invasion in any meaningful way - all the player can do is build defences and hope Chaos don't dump all their stacks on your cities. I think some extra layer of strategy would be welcome here - if the player can possess or raze certain provinces in Norsca or the northeast of the map, the Chaos invasion will be weakened due to a lack of supplies. Why can't I bribe the Chaos leaders to attack my friends first, buying me some time but suffering a major relation penalty with my former friends? Wouldn't it be cool if the player could somehow reform the Norsca tribes so they end up opposing Chaos instead of supporting them, so they could act as a buffer zone between Chaos and the player.
I understand the need for an endgame challenge so the game doesn't become a steamroll. However, simply dumping x number of stacks on the player and just saying "be prepared" is lazy. Some extra tools to manage the invasion would be great.
I'm aware of the need to balance lore and gameplay, but I believe gameplay should always triumph. I'm a novice at Warhammer lore, so cannot say if CA have used lore as a justification for lazy game development, but I do feel the Chaos Invasion could be better implemented.
Regards