There are so many great ideas for improvements on the forums.

This is another good one, having the cool downs shared really takes away some of the strategy. Because most fights are over before the cool down finishes, giving you really only one potion to pick from.

Also splitting the potions up in to different groups with different cool downs would make fighting with ranged/magic a lot more exciting, especially for low level classes (below lvl30). Often you find yourself sitting there spamming buttons whilst the tank takes all the agro, imagine if you had to make more decisions about when to cast different potions and on whom.