took rengar against nasus today
sure, i couldn't stop him from farming very much, but do you know what i could do? relentlessly gank other lanes with my stealth, and split 1-2 turrets in a minute with aa resets from q+ravenous hydra.
not sure why rengar doesn't get played much at top to be honest. its very easy to build up 5 stacks and have an empowered ability, and his damage is pretty solid.