Respecced my characters (via the respec potion mod) and tried the broken tactic of the game:
fighter goes towards enemies, pulling aggro -> taunt -> mage casts force field -> all enemies now try to hit the un-moving fighter -> storm of the century where fighter is.
So very very broken and I can see how having 2 mages in the team is a potential for some really bad broken design. It makes the game dull since taunt->force field works on any level of enemy due to the stupid AI design.
So I respecced again - respecced Morrigan to be an offensive caster with only cone of cold as the crowd control spell. It's working out pretty nicely so far.
It made for a far more traditional RPG game where the mage holds all the most offensive options but require the fighters and rogues to hold down the enemies while she casts storm of the century on the unsuspecting mob.
I still do the usual taunt to group the enemies together for the spell effect, but instead of using force field I use anti-magic ward (it's like a much shorter version of force field and doesn't protect you from physical attacks).
So far it forces my party (PC d/w duelist rogue, templar tank Alistair, bard archer Leliana, offensive mage Morrigan) to use all bag of tricks and items to beat the difficult battles in the game.
It really made the game much more fun this way - the joys of seeing a rogue throw out 2 bombs on a group of enemies before backstabbing the mage, have Leliana do scattershot, Morrigan does blizzard, and then having Alistair the tank go up to the enemy mages to cleanse magic with anti magic ward is fucking awesome.
It really is a much harder to earn fight but it's really cool seeing how useful the items crafted throughout the game are (rock salve, various bombs, various poisons, cold resistance salve).
So to all those who say mages are too easy to use, yeah, the broken game design makes it possible so don't combine the broken spells since it will just make your gameplay experience very boring.