[Habibi Jones]

anyone can tell me if the potions all have a different timer? [Yes, they do. I had the cooldowns for mana and greater mana pot on a piece of paper that I apparently threw away ;p Greater mana is the highest, GH seems the be the same as lesser mana. Invis and refresh potions also seem to have the same timer as lesser mana and GH. I'm not positive about the values, though.]

if so is it more beneficial to use mana potions rather than Greater mana potions? [In certain situations, yes. For PvM they are much cheaper and when used with meditation are a much better alternative to totals. For PvP, they are useful because sometimes you will need less mana than a greater mana gives, and don't want the long cooldown for the next potion to become available.]

are there any pots that has a seperate timer like cure pots or invis? [99% sure every beneficial self-consumable potion is on the same timer]

^^