As others have said in different threads the percentage number to hit should be an unknown when you first encounter a new creature. You are not supposed to know its AC, Resistances, ect.
The solution imo is what they do in alot of other games, make a Bestiary of sorts to keep track of known information. Where at first you dont know the creatures stats at all (maybe not even its name, that that might be to much) then as you attack it and test abilities on it you learn its stats. I would tie this to difficulty since im sure many newer players would prefer to just see the %. Likewise you could find lore books, talk to NPCs or perhaps make nature/religion/arcana rolls ect to have a chance to learn a number of the creatures stats. This is how it is done at the table in DND and i don't see why it should be done differently.
By showing just your Dice Roll and Bonus (i.e. 12 + 3) you would not be showing the AC of the target
