I was thinking of posting this a while ago, but yeah, I 100% agree with this.
Need to also have a /playerfocus where your targeting puts NPC mobs at lowest priority and all players above.
And to avoid the complexity of commands, it could instead be a toggle that cycles through all the priorities (like run, pvp, etc.) that is shown in a part of UI (if enabled in the Options menu, just like how you can see your Run/Walk toggle on the UI).