That battlemaster manoeuvre doesn't have any forced movement tied to it in the dnd rules. It just deals bonus damage, applies disadvantage on attacks while the target can see the fighter and prevents the target from moving closer to the fighter (which can be useful when your fighter uses polearms). So of course adding forced movement to it was too strong.
But dissonant whispers doesn't apply any disadvantage to the target and deals less damage than other first level single target spells, so the movement was the main reason to cast it.
Many of the deviations from the DnD rulse that Larian added make me think, that they don't understand some of the DnD rules and why they are needed for a somewhat balanced game.
