The most common and the most infuriating bug with formations, that I've experienced, is unit freeze.  To reproduce: 1) Make sure "No override" is selected for formation control  2) Order your units into a line formation,  3) March towards the enemy base,  4) Add some more units to the group from your base,  5) Attack move the enemy base.  Half the time, most of your units will just sit there frozen, while a few march in to be slaughtered by the enemy.

I’ve had matches crash unexpectedly too, and yeah, not being able to save online games mid-session is frustrating. A mid-game save option would make co-op and long matches way better.

Some formations should give an advantage to the defense and others to the offense. Testudo vs missile firing. Phalanx similar but less protection and some attack 2% more maybe  Close formations should have bonuses against falling arrows and other projectiles. Syntagma and Anticav would be bonus to the attack against cavalry. Closed formations should penalize movement and open formations should favor it. The Persians were to have a unique formation, which would serve as a shield and barrier to the enemy of archers.( Protect the archers) It would be a composite formation. https://archeryhistorian.com/persian-archery/#:~:text=Persian Archery %26 Battle Tactics&text=They would release arrows%2C and,units would form their lines.  

There is still at least 2 different bug with formations that I haven't been able to have clear way to reproduce yet too. 1. is units acquiring random targets when pressing Halt in formation, ex: a building even if clearly there are units nearby, or attack units far away. (happens when there are a lot of entity around so i guess it's because of some optimization stuff) 2. units sometimes freeze/dance salsa endlessly in formation. Else wise, formation are already very very useful without bonus already, for unit placement, and to fight efficiently. I know some will consider bug too but it's actually nice that units can cluster up while in formation. 

There is a need to normalize the formations.

@real_tabasco_sauce 1. "units don´t actually fight in the formation" wrong, if you put your troops in front the enemy´s units they will fight while maintaining formation. 2. The battle formation exist to be an advantage in battle, no one chooses battle formation for cosmetic but for win. 3. Bonuses are not rare in this game, for example range bonus: ir you build a tower in high ground, it´ll have more range. I don´t see how complicated the solution I´m proposing is.

units don't actually fight in the formation, and selecting a formation over another just for the bonus and not for the formation of the units is gimmicky. I think formations are fine to remain as-is for organizing troops and for cosmetic reasons. There are more straightforward ways to address the issues you raised, like some speed balance and diverging the different roles of units.