Kitty Kitty Boom Boom was ecstatic to hear of this change from a recent RIFT Livestream: "According the Bill Fisher (Daglar), the reason is that the vast majority of RIFT players dabble in different things. The subtext (in my opinion) is that not enough people are getting to raiding. They'd rather do a little of this and that -– in other words, have fun. Going forward, whatever activity you choose will contribute to a background feeling of progress. This helps the raiding agenda while also helping casuals have a progression track."
Other adjustments coming with the expansion is a power cap system and a transformation of the tanking toughness stat into the DPS hit stat.