So from my understanding the turns happen all at once, so when I send the strand and I to 'hit and run' on an enemy the enemy get's to attack us as well correct? Assuming they're still alive that is.
Well they still get a shot even if you wipe them out: dropping them to 0 HP does not remove them from the field until
after the round is over. And remember, you cannot hit and run very easily: Once you became adjacent to an Enemy Stand, you
cannot move unless you take the Retreat Action, which means not attacking.
So, you can smash into an enemy, attack, take the attack in turn, take the Retreat action next turn and run away, then attack the following turn, if you wish. Or, you can just stay in Melee and grind down the enemy until you can eliminate the Stand and move again (although Units get to fill the gaps left by dead Stands if they have extra nearby).
This is why the Hetairoi are such a massive boost to Heavy Cavalry, because the ability to Paralyze the enemy basically means you can crash into them once and wipe the enemy stand from the field in basically 1 fell swoop,
and the enemy cannot attack back.
I tried to build as many of the "Elite Units" with abilities to manipulate these rules, like Mangudai basically always being able to stay out of range of most units, never get tied down unless surrounded, and yet
still getting their attack, or Hoplites and Vexillari in the same Unit basically forming a super Infantry Block that's going to take a lot of punishment and keep coming back unless it's picked apart by Missile Troops, and even then that will take awhile.