I would agree you need to be able to move rather then lock in a bad spot. But they could make a spell 4x the damage and rather they upping the cast time they could up the "global cool down". This would still give the effect of less spells cast but up the amount of DPS and give you the freedom to move. Another option would be to have an Aura for wizard that multiply the damage of your spell based on how long you gone with out casting. It would be like your charging up a spell for a bigger bang. Each server tick could and a counter to the aura and when you cast a nuke it will add damage based on the counters and clearing the counters. that way if your chain nuking you do X damage but if you hold off chain nuking you can make things go BOOOOM. the wizard could then decide do I hold for max damage or fast cast to finish something off.