You're wrong, it lowers your target's defense when you have your accuracy higher than 100.
Way to noob it up, bro.
Specifically, as per the loading screen tooltip:
Accuracy over 100% will REDUCE a target's change to parry/deflect/resist an attack made by you.
Basically, if you want WoW terms: Accuracy = Hit + Expertise (when you break 100%). A Sage/Sorceror does not require any accuracy for 100% hit chance with force abilities (if you wanna run up and melee, you only got a base 90%).
HOWEVER, this does not rule out the enemy Resisting your force attack.
100% Hit Chance = All Force/Tech attacks will Hit, but the enemy still rolls to Resist.
110% Hit Chance = All Force/Tech attacks will Hit, but the enemy still rolls to Resist, if they have more than a 10% resist chance.
And obviously, this is irrelevant for healers. Healing doesn't miss.