Sure if her q+w+r+r doesn't kill anyone she becomes useless basically and dies, but can't you say that for any melee assassins with a few exceptions like zed, if they blow all their cd's and don't come out with one kill, they're dead the moment they get focused. That's why assassins will have to wait for the right moment to jump in.
If you're saying she needs tankiness + damage in order for her to do her part in a fight, I take it you're one of the people that build's nashor's tooth on her.
Get her a lich bane and a zhonyas or abyssel scepter, play like a jax in lane, aa a minion twice, q an enemy, if it hits, r + aa you've dealt quite an amount of damage.
If you're going to talk about teamfights, like I said you gotta wait for the right moment so until then you'd just keep spamming your q, Her aoe is decent when it comes to poking and does quite the amount of damage. If you decide to go in, open up with r, e before w, if you managed to get a lot of people to pull in, your e will deal decent aoe to everybody, but the person you targeted with your r, you got yourself a powerful aa with lich bane, if they start focusing you zhonyas. If you ever manage to proc your passive during this fight (Like doing the aa tactic on minions) you'll deal quite an extra amount of aoe.