Can't comment on a unreleased class, but the skills ingame so far have been demonstrated on other games with FF enabled, and it has worked out great in those. It brings a lot of depth to strategy, placement, situational awareness into play. I can understand if the goal of the game is to keep it as simple as possible to bring in more of the lowest common people in, that this suggestion would be a step in the wrong direction.
I have trouble understanding your thought process with your example of megabolt. I'll give you an example scenario to help you out. You and your group are about to face off with an enemy group, You start off with a blizzard focused on the center mass of the enemy group and move to use megabolt, and now melee are clashing and you switch to things like fireball unless an enemy brings enough room into play for you to use an aoe on him.
This isn't a new concept and has been played out in several games, with nearly identical skill mechanics. I believe your fears are unfounded.