I do have wonderful nostalgia for Sneak & Invisible from FFXI, but I can understand the Development Team's decision. A Sneak and/or Invisible ability would be ubiquitous in an Armory System that allows players to equip any ability and an environment that allows for passive MP regeneration.

Everyone would just level the appropriate mage class to get the ability, like most every player did with Cure and/or Second Wind.