The design perks are quite difficult. I haven't played the game enough to know what exists and not. So when designing a henchman I have to guess on skills, when coming up with a summon I have no idea what kinds to chose between and I have a difficult time with the "Personal Dual Dialogue" (don't know what kind of structure it has to be in) and "Design An Item Combo" (have no idea which items are in the game and how they combine). I wish they provided more examples and a clearer description.
I couldn't agree more. There have been numerous threads back as far as when the Larian Vault KS form went online asking questions to clarify all sorts of things like the points you raised. At one point I tried collating them all into one post/thread (I even colour coded it to hopefully make it easy for Larian to address people's common questions) but AFAIK we never got a response.
I had assumed some more details would come later but it appears Larian never managed to find the time/didn't consider this a priority. As a result I found the experience a bit frustrating and didn't even do the personal dialogue at all.