Shoving to knock someone prone or 5 foot away from you is very niche and its not as powerfull as it sounds. Not to say that it isent powerfull though. Knocking someone over in melee range gives everyone around them advantage on their melee attacks. Which can be incredibly powerfull if you know other friendlies are up next in the initiative order.
Grappling also isent in the game I believe (or rather dident see it lat time I played) and that one has alot more potential impact on the game. Specificly because some monsters use grappling as their main form of attack. So long as grappling isent in the game, those monsters cant be either.
But before I reel of topic more.... With multi attack they should just overwrite a single attack, not all of them. Each of the moves (grapple, shove, knock prone) specify that they replace a single attack. Making is so that it replaces all of yyour attacks is a MASSIVE nerf to martial classes.
