Could you arrange a meeting with your boss; not to moan about these two but along the lines of 'obviously I want to my job to the best of my abilities, so can you help me clarify my priorities so I can best help you and add to the overall success of the business' (or words of your choice!)

This makes you look good, that you are thinking about your job and trying to help your boss. In addition if the two witches try to pass over their work you are quire clear about what you should/should not be doing. Any additional duties would have to be run past your boss - that might scare them off.

I know you don't feel very brave at the moment but try and keep any conversation strictly to tasks and avoid any personality issues.

Good luck!

Carey