All of those are pretty strong in fight(voli's W would be great CC if we wouldn't have such a massive CC creep esüecially on tanks), nunu's has good passive effects and a really strong heal, though conditional. it would be great if he could consume heroes for very small damage to get atleast half the heal.
(edit: forgot about the buff stacking up from eating monsters, that one should atleast affect big minions or, if implementet, from champs so he's not bound to the jungle that hard. However, it's well possible to take a camp as lane/support nunu every now and then to keep the buff running)
Hecas is actually just as usefull for heal in lane and the most effective in teamfights...
There are certainly champs that are held back overall because of ther jungleing, but those 3 for me aren't the case, with nun beeing gray area.
Things that allow really fast jungle clear ad then balance the champ around haveing a default gold n xp lead imo are what really holds back some champs like Nida or Shy. Because of their insane clears, they are balance in a way that they need to be ahead to be of any use, as it's seen as their default state. If they break even they basically loose, and if they fall behind they are just usless - which also means their endgame is pretty bad as endgame you are always even.
This also mostly kills their laneing and atleast for Shy who has not much ganking preassure it really puts her into an ankward spot.