it would help out, probably strategically for pvp too, that skills should be separated into at least two different types. each type has its own independent GSC.
example: (using a mage)
-offensive and defensive
while you cant cast attacks like fire or lightning off at once, you can suddenly put up mana shield right after a fireblast, considering how after damage such aggro coming your way should be handled rapidly. same for revive... no matter what attack you just casted at the enemy, you should be able to save the team before you also fall. debuffs count as offensive, so no worries about quick eliminations. this is a survivalist approach. might lead to saving defensive spells for emergencies instead of just part of a sequence, since you never know when sewer gas will cause a almost-wipe.
-health affecting and not health affecting
more subtle IMO, skills that deal with health such as fire, drain hp, heal or rex (brought to life) have their own GSC while the rest, mainly debuffs and buffs, are separate. makes you choose between healing or hurting, weakening the enemy or fortifying your friends.
the general outcome of this is so that you have a slightly more interactive skillset with real time tactics (mainly pve) and so we can have some of the previous pve manslaughter/survival we all love.
also, for those who think that the GSC is for more strategy in game, i disagree. now, more than ever, i am simply following sequences of spells. having multiple GSC timers could lead to being able to change the strategy mid flow. much harder in our current linear system.