Quinn player here.
Here's the thing: Quinn's ultimate isn't an "I need to use it on every chance" and so are her spells. If you chew through mana that fast that one ult means you're dry, then you're playing the lane wrong.
I don't have a mana problem because whenever my opponent backs, be it willingly (he pressed B) or forcefully (respawn timer), I either back on the spot or shove the wave and back, depending on how much mana I had to use to make the opponent back. Even against Teleport users it's not too bad.
You're ranged, punish their every auto and cs with your autos and keep your spells for either Electrocute combos or to deny a cannon minion.
For how strong Quinn's early is, I don't think she needs a buff as huge as that.