The game has been out for long enough for the novelty value to wear off. Provided you buy hearsay the reports I get are sadly roughly as bad as I fear wrt the campaign AI:
- Naval invasions seem to be absent, as is naval transport.
- All artillery stacks are common among some factions (notably the Mughals)
- The AI splits its navies into multiple small stacks that are easy to handle piecemeal.
- The AI sends small stacks into enemy territory rather than larger stacks (fine for raiding and economic warfare, but not so good for full blown invasions).
- The AI wont garrison it's capitals or go for enemy capitals.
- Some minors are awfully belligerent and attack major neighbours they cant possibly beat.
On the plus side diplomacy and alliances seem fairly robust, but flawed patterns in that area takes longer to discover, so I'm not counting on this to hold.
I'm just finishing up my first foray as the Russians in the Grand Campaign and I can speak to your bullet items above.
Naval invasions indeed do not happen in the current version. To be honest, I think they removed that for balancing, as it would be very difficult to play many of the chosen factions if naval invasions were in. For example, most Euro-centric nations have enemies on all sides from very early in the campaign. Adding naval invasions would simply increase the enemy invasion routes exponentially. Do I agree with this on a historical/realism basis? No. But I can appreciate how play testing would've caused them to remove that feature, if in fact it was ever in there to begin with.
For artillery stacks being the same, I haven't played the Mughals but this wasn't the case with the Russians, as I distinctly remember having different forms of artillery in my army at a time.
The Navy AI does seem to favor lower-level naval ships over waiting on the upper-class ship-of-the-line ships, as I did. Hence I was able to easily decimate a large force of AI ships with only a couple mid-level frigates, as they simply couldn't stand up against my broadsides.
The AI does still send in small stacks in an attempt to wear down opponents economically, as it did with previous TW games.
I'm not sure I agree with the lack of garrisons in the enemy capital. I just attacked Warsaw and went up against a formidable garrison, complete with sandbags and other on-field fortifications. I won, but it was a bloody affair.
The minors can be easily placated by simply giving them technology. I think they made the minors active to force you into more diplomacy.
Overall, all of your points are valid. There are problems with the game. In fact, the battlefield AI is borderline stupid at times, especially when being harassed from afar by horse archers. However, even with all of those things (and several more) taken into account, I've experienced more sheer pleasure with this game than any of the previous outings. Some of the land battles have simply been "epic." In fact, I've experienced some battles in which the AI actually did the magical thing of being creative. For example, I nearly lost a battle when I lost track of a group of hidden enemy cavalry who circled round to my flanks while the battle was raging and wiped out my artillerymen. I've never experienced such creative flourishes from the AI in past TW games.
The campaign AI and gameplay is pretty much the same as before with diplomacy taking on a more central role. Blocking of trade lanes is far more important this go around as is the necessity to break through these trade barriers to keep from going bankrupt.
So, if you hated the AI in previous TW games, it is better but only slightly. However, if you can look past that and enjoy the game for what it is, there's a lot here to like.