Arguments against RNG:
The current video game market do not like RNG much, Julian Gallop's remake of Chaos: The Battle of Wizards, one of the best RNG management strategy game in history, got bad reviews by players largely because of this.
For singleplayer, the player would usually reload battles lost by bad luck, but not the ones won by good luck. He ends up cheating in a sense even without save scumming.
For multiplayer, to get a fair outcome you need multiple matches to approximate statistical average, which is several times more time consuming.
Calculation in any complex deterministic game is already largely statistical, have you seen how a advanced Go/Baduk/Weiqi AI, such as the ones beat the top players work?
A game that has RNG got bad reviews is not an argument against RNG in games - If anything the market shows the exact oposite, easily checked by looking at which games with tactical combat have a higher player base, and this is not an argument in favour of RNG either, just sales.
A player can reload battles lost by bad luck is also not an argument against RNG, you can do the same without RNG, this is just illogical on several levels. Not to mention that savescumming is a player side choice, the game has nothing to do with it.
Multiplayer is not the case at hand. But this statement was also false, there are several multiplayer games competitive and not competitive that rely on luck on different levels. That are widely played, and that are not so much.
Realism is actually an argument in favour of RNG, combat does not have deterministic results or foreshadowing. Not to mention that those AIs have very specific purposes and you won't see them in complex games in the near future.