Therefore, unless you don't mind losing your entire stack, and only getting the given odds of killing one defender, don't use stack attack. You wouldn't trust the AI to run your civ, so don't trust it to manage your stack in battle...
Further, I strongly suspect this is standard Civ/BtS behaviour. If you try and think like BtS AI
, you'll realize the explanation is along these lines...
I don't want to lose my entire stack per battle, that's why I stopped playing C2C shortly after I updated it so long ago!
In CivIV vanilla, Warlords, BTS, and every mod I've ever played - the game would always send in the unit that had the best odds of surviving
(With the exception of when Drill promotions were bugged). I couldn't trust the AI to run my empire, but I
could trust it when it said I had a 99% chance of killing an enemy archer defending in a city. Not anymore - now it wants to send in the spearmen I had following me protecting my units from Horse Archers instead of the City Raider IV swords. Yeah, in that situation I could just go in and manually send the swords in, but out in the field when the AI is marching around a large number of mixed units with varying promotions, I don't want to spend several minutes shuffling through my troops trying to see which ones actually get the odds the game was showing me - for each and every time I attack - every turn until one of our stacks are dead.
I never had to do that up until that time I updated C2C. In any other mod and in Civ unmodded, I can at least trust the combat odds that the game displays to me. I can't trust it in C2C anymore. I've never been a micromanaging sort, with the possible exception of my capitol or when I'm prioritizing a specific Great Person from a city, so I really grew annoyed when that sort of micromanagement became seemingly mandatory for every battle I took part in because I couldn't trust the combat odds the game displayed to me.
It's not that bad in the Prehistoric, Ancient, and early Classic - but once it gets into and past the Medieval it just gets too tedious for me to handle and I start a new game or switch mods. Even in AND and RI, once it takes ten minutes to pass a turn I lose interest in the game I'm playing, and when that time gets doubled on because I have to pick through dozens or hundreds of units every turn, I don't even want to continue at all. I hated how the Stealth Bombers had such massive range, and shuddered at having to direct them all over every turn until I realized there was an Automate Airstrike function.
I really like how this mod plays, raising a mighty empire out of literally nothing, building it all the way up from the mud and into an interstellar civilization - it just fascinated me. I don't like however having to manage every single unit every single turn. A little bit of assistance from the AI to me is a good thing. Automate Explore/Spread/Hunt, the City Governer for non-critical cities and ones not building Wonders... "Hardcore" players may avoid these things like the plague, but I find them critical for me to enjoy such massive games like this. If all the automations were disabled and you were expected to hand-manage every aspect of the game for every turn and every unit in your empire, I wouldn't even bother. That's why I got so frustrated with this combat 'bug' - because that level of micromanagement was just tiring me out and severely killing the fun factor for me, and as I pointed out - no other mod or base Civ had that feature, and the first version of C2C I tried didn't either.