For armorer, leatherworker, and weaver (and goldsmith as well in some cases), can't you just run dungeons for i70-i80 gear? This also has the bonus of getting you philo mats to craft other i70 stuff, so even if you don't get the gear you want for desynth, you still get something. If you get gear you can't desynth, just turn it in for seals. This is quite an ingenious way of promoting people to run more dungeons, along with the myth reward increase.