Q is like any other skillshot. If you can predict your opponent's movements it's fine. Or you can use it in conjunction with ally CC to stun people forever. It's probably her strongest skill outside of her ult.
W is mediocre, but not a bad skill for early-mid game. Much less mana intensive than other heals out there, and it does damage at the same time.
E is actually good, but nobody realises when you give it to them. It's not necessarily a carry booster, since it only lasts 3 shots anyway. Sometimes it's better to give it to someone who can actually use the slow better, like maybe your bruisers.
R is strong, but needs thought on when to use it. Tossing it out randomly and hoping it'll initiate is stupid. Using it in a narrow pathway (ie, the jungle) makes it much harder to dodge without blowing flashes or wall blinks. Using it in conjunction with an actual initiation spell on the other hand, makes it amazing.
She needs team co-ordination to shine. So she probably does feel useless if you're playing with randoms.