Is rengar still good?

yes he is good

IMO hes a better top laner than a jungler as his Leap is kind of situational, you need to wait and hope they get close enough for you to leap at them. till you get your ult. his heal helps him stay in lane a little longer and his E makes a good disengage/ engage depending on how you use it.

pro's: manaless good lane/ jung sustain good single target burst good lvl 6 gap close ganks gets buffs from kills/assists

Con's: weak escape tool (his ult if you have the edge of distance) very susceptible to a heavy CC team skrimish outcomes depends a lot on your ferocity stacks, the more you have, the more you're likely to win and vice versa.

Watch Ryan Choi play Rengar. He literally takes Rengar any lane, gets fed and carries his team to victory. He usually gets first blood around the second wave of minions.