I agree they definitely need to adjust something, but as it stands now, Empyreans are actually cheaper to buy outright than Mythics are (on average on my server).

Alexanderite (buying all 30,000, not farming ANY) is 210 million~
Plus ALL the legwork you have to do
VS.

HMP (buying all 1,500) is about 105 million~
Rift item (buying all 60) is about 72 million~
Totaling 177 million~

(At these costs you can make 4-5 relics lololol)

Now the biggest difference is that HMP and Rift items is much harder to farm in bulk and in turn are far less seen floating around on sale, since most people that have a lot on hand are probably saving them for their own weapons.

They should make HMP/Rift available to farm in other ways (Abyssea?) or making them drop more often/in greater quantities (maybe via proc) since it seems they don't want to lower the set costs. Maybe the update to REM will breathe new life into Voidwatch and HMP/Rift will be seen more. Probably not.