I agree with the general upbeat nature of comments

Rather than debating the nature of best defense in an impossible situation (sometimes charging out in a blaze of glory will be be the highest chance of a win out of defeat, other times turtling is best), I'm much much more interested in the AI keeping formation right up to battle

One of the biggest problems with TW AI in the past has been that it breaks formation to engage so that where you might lose terribly against a particular AI army had it kept formation in attack, it breaks up & attacks piecemeal resulting in a victory for the player.
Particularly so in the case of a pike phalanx army.
If this is now fixed, then single player is now going to be much harder I think

Now if the claims of improved diplomatic AI also stand up & it is actually possible to have an angry AI cowed into a reluctant peace by a string of defeats, then this will be a game really living up to the billing!