While a bad nidalee can be a burden on your team, its the same is for any champion in this game...
A nidalee who can't land spears is perhaps the most useless champ in the game.
She will still have a trap that debuffs armor and mr and reveals for like...ever (like 10 sec or something) as well as an AS buff for her carry even if it doesn't heal a whole lot. Those are pretty nifty in supports.
Support Nunu is similar really...AS and MS buff for carry, AS MS debuff for enemy. Better? Usually, but they ARE similar. However, during laning, Nid can harass a lot better, using the same amount of mana for chucking spears as iceballs, but also having a ranged AA.
Nid can also be a good decoy if you're low hp, the enemy WILL want to chase you. Fortunately, Nid is pretty good at escaping. Them chasing you will either get them killed or at least free up your carry for a safe exit.
I feel like you're not looking at all of this with an open mind.