How to avoid ganking on 3+ vs 1 encounters?

Is there a way to make it so that on mobs of 3 or more enemies only a portion of the mob goes to attack while the rest stay on the back? Just to add some variety to enemy behavior, and to not overwhelm the player, as the party is meant to be made of one actor most of the time.

You can set enemies behavior to just guard for the first turns. You can do it in the Enemy tab in your database. Of course this solution is not perfect but it might somehow help you with what you are trying to do.

Keep in mind that you'll have to use the "slow start" version of your enemies only in troops with 3 or more enemies. I'd recommend to create two version of those enemies so that you can have a "fast start" and a "slow start" version.

That's actually a pretty good suggestion. Yeah, it's not perfect, like you said, but I don't mind adding enemy duplicates in the database, and it's pretty simple too ;w;
I haven't tweaked that many things in the enemy info in the database, so it's no wonder I couldn't even come up with something that simple hahahaha.
I just tried it and I guess it does the job, so I'll stick with that.
Thank you very much! Cheers~