How many times are you going to say they don't need devourer? Because it's like the 3rd time you have said this, we get it.That being said devourer is magic damage when you have an all ad team so there maybe instances when devourer would be a good idea
Stealing objectives is actually quite easy, eye the health and how much your smite does. I've done the baron steal with a few different champs, the hardest is when you are ADC, possible but very difficult.