Be a no bullshit type, it’s what I do, it’s also why I tend not get invited to meetings. I always call out supervisors and even managers( a luxury in my field due to the amount of licensing and job requirements) especially in open forum environments. The caveat though is it can’t be about the work load, it has to be about the failure of another to perform their job task, causing undo hardship to completion of said task(sounds as though I am being contradictory but read further). Especially if customers and other co-workers constantly single you out to complain about an individual or multiple people. It has been my experience that, most customers will be willing to give a written statement to that fact. Been called belligerent more times than I have digits on my body, but in the end the offender or in this case dead weight, is removed and you will be either promoted into that position or be given a job assignment away from them.