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.
Yeah that sounds about right. Fast units made a poor early impression on me during the middle ages where they tend to charge halfway the battlefield and then get carved to pieces. That was from watching the AI using defending armies, because I didn't use them too much at first. Their main use early is to counter large numbers of ranged units, and even then under auto it seems to be a toss up between using the fasts as intended or countering ranged with other ranged. Eels are probably the one fast unit I can think of offhand where the AI doesn't screw up too badly, but the AI does seem to handle stealth decently well.
Using rogues usually involves sending a unit into a corner anyway, especially if it's a two wave fight to avoid damage.
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).
I've seen plenty of AI mistakes which is why I avoided using it until my stats were so high it didn't matter.
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.
IIRC, Blast gives a bonus to damage when the unit is closer to the target, which is probably what the AI is trying to exploit. Blast first appears in Indy, where almost everything has a ranged attack, so going into melee range is stupid because the unit is needlessly taking retaliation. Though I'm not going to do complain about artillery doing it, because Plasma Artillery is about the only unit I find threatening again Hover Tanks.
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
They're manual only because everything about them is far too fiddly to trust the stupid AI.