the lack of support or communication re Attila points to CA having basically "moved on" in the sense that Attila is no longer the focus, Warhammer (and now Halo) are. 300 employees is not a very large number to work on a "Tipple A" game, while there will be a core "Total War" team they'll need additional support from artists, level/city designers, coders and testers to actually make the game. Now we have a situation where CA is producing three RTS games, and if both Halo and Warhammer have been announced that means they've been sucking up resources for months if not a year or more - which may be why Attila gets little attention.

In answer to the OP - CA jumped the shark when they sold out to Sega. M2 was very poor quality at release, Empire had rubbish AI, Napoleon was a little better than Empire and then R2 was just a joke, so much so they had to remake the game almost from scratch after release.

So, to recap, since Sega acquired CA after Rome I, four out of six games have been sub-par at release (Attila and Shogun were the exceptions). CA has got away with this, to a point because of their long dev cycles - I read one review of Attila which praised the family tree and traits and compared it to Crusader Kings II because the reviewer didn't realise that the family tree came from Rome I (and worked better there than in Attila).

Diversification is a worry for another reason because as CA diversifies they are less focused on Total War, which dilutes the expertise in making Total War (which has been a problem over the last decade to begin with) as CA becomes less distinct and more just another RTS maker they become increasingly vulnerable to being shuttered and having their IPs split up and either sold off as surplus to Sega or diverted to other studios.

Now, that will happen, it's when not if, and if you don't believe me I suggest you look up Westwood Studios, or Ensemble, or Origin.