Needless to say that there is a wide range of prototyping tools out there and I won't say which one are the best ones because there isn't one. I liked to say it all depends on your workflow and what's your purpose of this tool.
We all have our sort of metaphors of what exactly is an Art Director and what does it do exactly. Our image of ourselves as Mad Men is hugely not realistic but in fact, they do much more than what others will think. From the beginning to the end, Art Directors should be involved in every step of the way. From the client first contract, mapping, wireframing, prototyping, figuring interactions, working with developers and making sure of their vision is showcased across the project.
About Matthias Mentasti
Matthias is an Art Director over at wild, a studio that is currently based in Vienna, Austria.
For more information: http://www.mment.at