The whole complain thing started in KR, not in NA, so make sure you look into the situation in KR, and not NA. Also, we haven't reach the episode that KR started complain about staff power, so I think it's unreasonable for any of us, to claim whether staff is useful or useless until we have played it.
Right now, staff's heal is still useful, and staff's damage is not severely below others. The whole argument of heal is pitiful, or useless, is based on player' skill. In a noob party, heal won't be able to keep up, therefore pitiful. In a pro party, no one will get hit, therefore useless. But what happened to the people in between?
I think very few of users here, can claim that they never get hit, right? Once got hit, depending on the damage, a player will have to decide to whether potting, or continue on attacking. Potting means taking away more time damaging, and continue attacking means risking your life. Staff, who can only deal decent damage once in a while, can take this opportunity and heal you, without hurting the party's overall dps.
Don't say that potting is easy or doesn't take too long. I noticed, in my solo runs, that if I pot a lot, I usually suffer in clearing time and also risk being hit. If I didn't, it would be faster, as long as I don't make mistakes again. Even in party, potting usually means aggro, if you're unable to finish drinking the potion before the boss reaches you, it means death. Now, staff fills in this situation. Her heal isn't enough to save you from that last hit, but is able to let you stay on the battle.
When KR players complained about staff heal being little (fix amount as opposed to 2k+ hp), trash clearing is painful (ep6 trash mob is really an issue), dodge not useful (well, we all know it's quite pathetic dodge); NA players took those complains and tried to fit those complains into NA. It didn't work out, there are still people who love staff and good at it. So people proceed to troll one another, and spreading the rumor "staff is useless".