Help becomes a bonus action

The Rogue can support an ally and still keep the action available for a weapon attack, Dash, object interaction that requires an action, or another legal action.

It helps the ally, not the Mastermind

The attack-related Help benefit normally grants advantage to the ally's next qualifying attack against the chosen target. It is not a self-buff for the Rogue's own Sneak Attack.

Range is the major upgrade

The Mastermind can provide this tactical assistance without standing directly beside the enemy, making the feature safer and easier to use repeatedly.

Bonus-action competition remains

Using Master of Tactics means not using Cunning Action with the same bonus action. Positioning should be planned so the Rogue does not need to Disengage every round.

High-damage allies gain the most

Granting advantage to a Paladin, another Rogue, a martial character using a powerful attack, or an ally who desperately needs one hit can be more valuable than using the bonus action only for personal movement.