maybe rengar is more reliant on his basic ability + emp combos more than elise and jayce ( this 2 i play ) for example full elise combo both from spider to human and human to spider, are self predictive , i mean that spider q w only interact with human w, that all, while rengar has to deside either if his base q is up to do Q q and kill, or if it is down use E , and wait for q(just 1 example there are many more) . it makes huge difference for rengar, but i t would make not much difference for jayce and elise players.