Yeah I mentioned that. Some setups are pretty easy to clear, and the AI is far too stupid to do it. It tends to be really bad with some types of units too, I've never noticed the AI to be any good with fast units, for example. Anything with a high movement rate seems to get charged in and cut to pieces early in the fight unless maybe they have an advantage.
8 Fasts that can hit first turn it does fine-ish with. If you need it to do a half-step on first turn though (either because you're using rogues or because this is an age where fasts can't cross the whole battlefield in a turn) you need to semi-auto. Go in, move the fast units where they belong the first turn (either a lone unit to the corner or many units just out of range of enemy units), and then hit auto to finish.
Of course if you blow the opponent out of the water in stats and are using rogues, that usually just means you use the heavy or light instead that won't wander off too far ahead of the rogues.
But to understand how the AI fucks things up you have to watch it battle sometimes. (i.e. go into a battlefield and press auto and watch the show).
Another common "seriously?" error: any unit with blast (and there are a lot of them - it's the most common "see through stealth" ability) it will try to maximize the value of that blast by going right into melee range with the unit - even if it means eating retaliation! all for what amounts to often ~5% boost worth of extra attack
Artillery with blast expose themself to more fire as well rather than hanging back out of range of some of the units still.
And on the topic of the thread in question, irritatingly missile artillery will *not* move forward extra squares on auto - so often there's only *1* unit in range of them and their special "hit 2-4 units" will be wasted and they'll despawn. Which is why they're manual-only
Good manual battlers make the best auto battlers too because they understand how the units work - and often how the ai works from watching it in comparison to what they'd do. Just the margin isn't as wide when the players have enough boost
The player that's put in their time on manual probably can push attrition a little further. And might lose a few less units at low-mid attrition.