I know the idea of a trial group finder has always been thought of as impossible since trials typically need people who know what they are doing and people who *do* know what they are doing don't necessarily want to train every new player. Here's the idea:
Trial finder is for specific trials. Unlocked per character, per role, per trial, per difficulty (vet unlocks vet and normal) once they have completed it x times (maybe 3? 5?). For example, if I have completed normal Aetherian Archive 5 times as a healer; trial finder for normal AA has been unlocked for this character as a healer. If i've done veteran MoL as a dps x times then normal and vet MoL is unlocked for this character in a dps role.