If Selene was truly going to get a rework I would want the Eos and Selene abilities to have separate cool downs first. Selene would have Embrace and 3 abilities on a 90 second cool down that is shared. So if you use any one of Selene's abilities you must wait 90 seconds to use another one of Selene's abilities. Basically Selene would come out and use one skill then be swapped for Eos who can use all her skills independently. Selene would still have Fey Wind but with a 5% speed increase for 30 seconds. Fey Vigor would raise the party's maximum HP by 5 percent for 30 sec. Fey Bounty would refresh MP and TP for 20 seconds. This way you would be encouraged to swap between Eos and Selene regularly for the buff from Selene and the healing from Eos. Dissipation would also be reworked to summon the opposite fairy for a free switch.