Ask that same question with any dps class. you can just bring hunters and not the other class. we can provide damn near any buff and debuff just by switching pets. our dps is not bad. and we can dps on the move without losing anything. so why not bring a hunter?
If your raid really needs you to bring any significant buffs, they failed at comp building. It's incredibly easy to provide all buffs and debuffs to a raid following the 5.0 buff/debuff consolidation and still keep a balanced comp.
You often see Hunters running with Tallstriders for their dust cloud because they have nothing else, and even that's not needed.
All Hunters bring is DPS. We don't bring fancy raid walls or heals or anything. We bring damage. But the damage we bring is mediocre at best and bad at worst. If you need ranged DPS, you bring in Warlocks to do metric tons of it or Boomkins or Ele Shamana or Shadow Priests who can provide comparable raw numbers while also having raid cooldowns to provide during crticial moments. We're being used as gear sphons to use the Agi Mail given Enhancement Shaman aren't in the best place, and to use the bows.
At least in Cata you could say you were worth bringing since you could go Survival for the 10% AS buff that was rare at the time.