I know many won't care for this - but I think it opens up some cool room for more fun, cosmetic, talent, set bonus and glyph alterations. Some new shiny visuals, glyphs to change appearance, talents and set bonuses to alter how Icicles might behave (store an extra charge, ability to release all charges in one go instantly, icicles could create an absorb shield instead of dealing damage, ability to fire Icicles at your Water Elemental to enrage it for bonus damage or to activate a special ability etc, ability to have icicles hit multiple targets for reduced damage, a bit like Fire and Brimstone - etc random stuff like that). The Mage class overall just needs more fun factor selling points currently (yes - I think the Warlocks stole the lions share of cool concepts and ideas this expansion).
Destruction aoe via Fire and Brimstone is incredibly fun. Personally id love to see a Frost themed Fireblast that could interact with icicles to (optionally) use them in an Aoe Rotation. Nice way to increase the versatility of the mastery.e) fireblast replaced with a frost themed version, along the lines of how inferno blast replaces that spell for fire spec (e.g., iceblast--super creative name)
"Iceblast: Instantly deals X damage and causes your next 5 Icicles released to hit all enemies around your current target for % damage. Replaces Fireblast". Or make it some version of Havoc, "... and causes your next 5 Icicles to also hit this target".
I like the potential for the mastery to be tied into the spec in new and exciting ways, even if we'd have to wait until 6.0 before we see potential big shakeups to doso. If Blizzard wanted, they could tie it into the spec with a neat resource style twist in a similar fashion to Soul Shards to Affliction warlocks.