I don't consider myself a 'crafter', but I do tend to dabble in crafting on any game I play. In my limited time (2 days) messing with the crafting in this game, here are some ideas I have (probably in random order as I stream of thought this post). I apologize for any of these items already discussed elsewhere:
I think a 'click-through' feature for sub-recipes would be amazing (see GW2). When you look at the main thing you want to craft, you should be able to click on the components to go to their recipes and craft them. After completion you can close that and be back in the original recipe to either craft that or repeat with other components. Even better might be if the grand recipe had the entire tree mapped into it and you could craft all its components in the same window.
Is drag/drop the best option for adding materials? Maybe clicking on the box and then you are given a window with only eligible materials for that box and you select one? Or at minimum you can select the box and your inventory grays out non-eligible items.
Failure rates are exponential, so you really only need a very small failure rate to still have a decent chance to fail at creating the greater items you are trying to make:
Item A with a 99% success rate, comprised of items B (99%) and C (99%) would have an effective success rate of 97% (chance to craft all needed items and final item without failure). This is only a rough estimate because if one component fails, you don't lose the other and have to only re-make the failed one, but if you fail the final item you have to remake them alI. I relate this to a poker tournament. To win a poker tournament, you have a very small chance to win if you put all your money in every time you have a % advantage in a hand. I would have to dig up my old Dan Harrington book to get more into this (I think it was his book), but he talks about one tournament Chris Ferguson won and broke down the odds of the hands he had to win. While the success rate on the individual craft might say 99%, the effective success rate really needs to take into account every sub-craft. If you take something with a 75% success rate and components of similar rates, you actually are very likely to lose your base materials in the process.
With that said, a player might be able to just buy / trade for the sub-components and not be working from base materials. Maybe this creates a market for somebody crafting at each tier so the high level crafter isn't wasting time on components.
I will have more thoughts, but I have to run out.