Adrenaline rush granted 100% energy but
in cata it stacked ADDITIVELY with vitality. In mists it stacks MULTIPLICATIVELY. It's not the same.
Cata:
outside of AR: (base + haste) * (1 + 25/100) (12.5 energy/sec at 0 haste)
during AR: (base + haste) * (1 + 25/100 + 100/100) (22.5 energy/sec at 0 haste)
MoP:
outside of AR: (base + haste) * (1 + 20/100) (12 energy/sec at 0 haste)
during AR: (base + haste) * (1 + 20/100) * (1 + 100/100) (24 energy/sec at 0 haste)
Someone with 25% haste in MoP has the same energy regen during AR as someone in cata who had 33.3% haste, which is one of the reasons why the AR energy problem is worse now in the SECOND tier of the expansion than it was in full heroic DS gear at the end of cata (the other primary reason is the fact that gems get double secondary stats).