I liked the way arcane played in wrath and wish they would have built off of that. They just needed to take away some of the RNG from missile barrage or give us a way to actively Regen mana without evo.
So with that said I would vote for changing our mastery to increase stack damage and revert the stacks to 4. Make the stacks more like combo points with a few finishers.. make nether tempest arcane only and consume stacks for more damage. Take away the proc on missles and have it consume stacks again. leave barrage as it is for cleave situations. Introduce a new spell that consumes charges for mana return for situations u get in trouble. make arcane power and evocate the same cool down for synergy. You could even have a spell to heal at the cost of stacks to give it a little more in PvP.
This would add more depth then what wrath had and we could have our burst back.. which is what made arcane fun