I like raid events. You can gain a decent amount of exp per raid orb and spend your precious nrg on farming TM's. Way better than farming/collecting events. Farming/collecting events do give better rewards, i'll give it that.
Raids are a good source of "free" exp/rank exp. Depending on the gimmicks or difficulty of the boss it can be really time-consuming and annoying though. Also the rewards this time aren't that appealing.
It's kinda tiring to do raids once a month. I'd rather Gumi bring back those dungeon events. I know they're not very cost efficient since they have no farming value and obviously takes more time to make, but we haven't seen one since the FF10 event since last september. Hope they didn't abandon these events altogether...