So I must have been doing my math wrong when I was looking at the new Replen numbers. After looking at the World of Logs numbers, having a replenishment is as good, if not better, than a mana cooldown (Divine plea, Hymn of Hope, etc...) for casters. Just looking at Argaloth, which was our shortest fight at 4:02, I gained back 25663 mana where as my average Divine Plea mana return was around 16k. With most of our fights being 5-8 minutes long, replenishment is going to be anywhere between 30-50% of a casters mana pool over the duration of the fight. Basically replenishment is still very useful, and needed.
P.S. Harkle you have to stay Destro, or convince Kilwenn to go full time Frost.