There are a lot of very nice skill interactions in the specialist system, the problem I see is that you have to put a lot of faith in RNG going your way to make use of it. As another mentioned, Trained Hand is a really awesome concept and I could see some very amazing symbiosis within the Whistle system itself. However, it relies too heavily on RNG going your way to be useful and I just don't see the Heart of the Craft being able to make up for it, at least with the luck I've had with it.