User blog comment:Nhan-Fiction/How Resourceful/@comment-4296199-20130208015935

The thing about the ferocity system is that it isn't just that system that makes it strong, but what skills are tied with them that are. Rengar's skills were alright on their own, but as soon as you reach the ferocity maximum, it was almost the equivalent of an ultimate. It was either a free infinity edge crit, stupidly large healing, or a root.

Also, there's the fact that Rengar repeats the skills again when reaching the maximum ferocity meter.

The main thing that was a problem with Rengar was that all of his skills were perfect for early game top. Q allowed him to outduel anyone that tried to fight him and the atk spd boost allows him to either mitigate attack speed lowering or help him beat down his foes, not to mention that the skill did crap tons of damage regardless of ranks on it due to it scaling stupidly high on his ad. W dealt good damage and gave good defense boosts, but with ferocity it gave him free powerful heals. With his E he could kite and he could last hit, while building up his ferocity meter and his ult either let him get the drop on enemies for free or let him escape ganks. Regardless of those situations, Rengar gets free ferocity.

I wish they had balanced Rengar's scalings better. They could have given a better reason to level up his skills other than for their basic abilities, like if you level up E, you get more healing, or if you level up Q you get increased damage.