Good use of Nidalee's traps just take a different mind set. Most champion abilities involve instant feedback of use. Nid's traps aren't meant to be used like that as a player would just get frustrated. They are meant to be used strategically not tactically. You don't get a big payoff using a trap in the middle of the fight, you get the big payoff using Nid's traps before the fight or the gank.
Think of them more like booby traps... you don't set them with the victim watching / right in front of you. You set them in anticipation.
Think champs are coming from a certain avenue of approach? ...put a trap there. Given their 2 minute duration they are great to set out in a dispersed cluster in your general area where nid will be for the next couple minutes of play. If you were in your position in the jungle or lane, where would you attack you from? Put a trap there :)
Another good thing is to spread them out due to the way the damage over time effect works. Damage occurs over 4 seconds so space them out in bushes or near walls corners / endcaps that enemy champs may try to squeeze next to in order to stay out of vision. Most enemies will miss traps in the grass :)
If you can sneak a couple traps in the enemies jungle bushes, often time the enemy jungler will miss them... depending on their current status, a trap can really give the enemy jungler a bad day. It messes with their head... Is Nid near by? Am I about to die to this monster now and have to back off so now my whole jungle rhythm is behind? SPEAR???
Most players won't recommend it but I find getting a Rylai's with Nid to be great. It's psychological. Most players are used to Nidalee traps being essentially worthless, but all of a sudden when they are slowed, the traps become important. In addition It's that little bit more of an edge to land a spear or catch up to them or get away from them.
I agree about the cooldown on them, wish that was lower. I'd like it if Riot increased the cooldown of the Spear (say 10/ 9/ 8/ 7/ 6) and decreased that of the trap (11/10/9/8/7). Machine gunning spears is what the unskilled do (also burns through mana). The idea behind the increase in Spear CDR would make players really make a choice about whether to throw the spear . I think that with a higher cdr plus the current smaller hit box plus the return of the older AP ratio would achieve the good balance that Riot is looking for.
Back to traps: Another underrated thing about traps is that they are cheap. So you'll burn through less mana using them, SO USE THEM :)
glhf
. That is their only use outside of applying her passive and getting vision of enemies. That and for clearing camps with Pounce if you play her in the jungle.