IvanZG, you're absolutely right.
Fastest solution? FTX needs to make all skills, previous, present and future, to be "set-enabled", i.e., able to form a set from.
They have to convert all skills to be set-enabled. It's the logical solution. Either that or delete the whole skills system and refund in gold the values paid for skills.
Also the dice system for changing skill slots in the sicarios , quite frankly, horrible. Make the change free or increase the amount of dice which are offered to mitigate this issue.
Lastly, skills generate a gold arms race, which was obviously the intent when FTX thought them up, but the players are getting tired of going round and round in circles which are paid for in gold...