i liked and support your idead, i have a suggestion too:
Q (savagery) Using 100% of the ad in the first evolution of skill, 110% in the 2nd,120% in the 3rd,125% in the 4, 130 or 135% in the last. (I'm not well defined about the last evolution).
W (roar of battle) before, I thought it needed the buff in damage, but changed my mind, I'd rather focus on the damage with Q, because if W receive a buff in damage, people will improve only it, they will start with sunfire and will be the only heal, heal, heal, someone told me about it and I ended up agreeding that a champ wich is only on heal is annoying, that's why focus the damage on Q, but i still guess that W should deal 50% more damage to neutral monsters and minions, to improve his jungle.
E (bola strike) I see no need for changes.
R (thrill of the hunt) could go to reducing the time rengar become invisible as rengar skill improves, so that the improvement in the third evolution he suffers only a delay of 2 seconds. Where: 3 sec in the 1st, 2.5 sec in the 2nd, and 2 sec in the 3rd evolution.
opinions are welcome ^ ^
sorry about my english, is not my mother language