Going to leak from PTRST for League

PTRST is the reformed group called the strike team that handles working with patches before they are released to the public. There are ranks/tiers for people depending on how various things aside from how much/well you play. 

Google League of Legends PTRST to learn more about it.

On to the leak (note that numbers are frequently changing so I won't bother trying to be exact)

Anivia's passive is being reworked to be a lot less disruptive in the laning phase. It's going to function kind of like Blitzcrank's passive. When Anivia falls below 30% she gains a shield that soaks [Base Number] + [% of AP]. If the shield is not broken Anivia gains 30% of her maximum hp. The duration has been bouncing around between 5-10 seconds. There is a new animation for the passive which looks like she has a transparent egg around her. It's really nice looking and it hasn't been reported to cause any FPS issues at all for low-end machines.

Akali is losing 2-3 seconds on Twilight Shroud (W) and losing a touch of base armor/mr. Riot said that she feels too powerful early-mid game in terms of survivability. She is receiving some compensation buffs to move her in a different direction though. I personally haven't played them but they are lowering the energy costs on Q and E as well as increasing the AP Scaling on her E (that is her AoE Blade Flourish for people who dont play her). The delay/cast time when using her E may also be removed, but she feels too powerful without it. It may not come out this patch, possibly next patch for that.

Morgana is getting an attack range increase from 400 to 510. (Same as TF now. She is definitely much stronger because she can last hit with much less risk.) There is also talk of giving her 5 more base move speed but I haven't seen it in game personally.

There are also a ton of changes to champions that have high base damage abilities that are spammable early game. Below is a quick list of what is getting changed. It may not be 100% the same when the patch is actually live instead of internal.

Malzahar's Malefic Visions is losing around 25 damage at each rank (not additive, just a flat drop of 25 across the board.) But he is supposed to gain .1 or .15 additional AP ratio on it.

Rumble is losing tons of damage on Q and R but given some hefty AP Scaling increases. He is definitely much less of a hassle in the laning phase.

Singed's poison trail is losing near half of the base damage but getting some nice AP ratio in return. Riot said he dominates TT and 1v1 top on SR too hard with his ability to farm/harass/become near unkillable and being obnoxiously hard to gank without a lot of CC.

Taric's base health is dropping by about 30 points but he is getting 5 more on health gain per level.

Irelia is losing the ability to apply item effects when using her Bladesurge (Q) but it now has a built in slow. The base damage was increased and the scaling was increased. The true damage on her W was changed to physical damage but the numbers on it were changed to have a higher gain per level up. it does not work with life steal or spell vamp (I was excited about jungle ~_~)
Her Ulti heal is now half from minions but its AD Scaling went up quite a bit. AP Irelia is pretty much left in the dust, even though it isn't good anyway.

Vladimir was retuned quite a bit in terms of base damage and being tanky all game. His Q CD is now 7.5/7/6/5/4.5 -- The base damage and base heal does not change when leveling it up (it's really low) but the scaling goes up every rank up (the scaling is absurd for a fed vlad.) he is MUCH EASIER to handle in the lane as a champ without a beast early game. Vlad is in a better position than he ever was. There is talk of not letting his Q proc spell vamp but instead of convert spell vamp into extra damage. They are working with new tech and in game mechanics so I cant guarantee its coming.