Rek'sai too Rek'ful, DEPLOY THE NERF BAT!
While I realize that this is a brand new champ and likely needs some retuning as a matter of course, this is simply beyond the pale. Rek'sai was originally billed as a low to moderate damage, tanky champ with a diverse utility kit. However, live play has revealed her for the true-damage dishing, infinite mobility, AoE whore that she is. Even WW, while still severely overbearing in both early jungle and mid to late game (due primarily to his ridiculous health steal) can't stand toe-to-toe with Rek'sai at ANY point during game play. Your best hope is that she hasn't gone back to buy items in far too long and is sitting on 8 or 10k gold. Then you might have a chance of trading 1:1 in a 3v1.
There are only a handful of champs right now that can jungle effectively, due to preseason changes. Among those, Rek'sai is the only one I have seen that can do it without any native health steal in her kit.
So, recommendations? Rek'sai should be forced to make some decisions with her kit. Obviously, high mobility is one of the defining attributes of this champ, and should ought to be left alone. However, there should be a certain level of reasonable risk to jungling, as with other champs, as well as risk involved in ganking and counter-jungling. To that end, i think that her over-all damage output should be severely curtailed. Particularly with regards to her AoE and True damage. Increasing CD's across the board might also make her more manageable. Bottom line, I think that Rek'sai should have to choose between her damage and survivability.
Just to show some comparisons, Rek'sai's 'bite,' has a 12 sec CD, scales on AD, and has the ability to deal true damage. Conversely, Voli's bite has an 18 sec CD, scales from HP @ 0.15, AND requires him to stack attacks before he can perform. I don't think there is even a LoL comparison for "Queen's Wrath", but who thought that a 4 sec CD was a good idea? It is practically always active.
Okay, I'm done with my rant for now, please break out your plushy foam weapons and go to town.