Counters and disengages. A decent counter to this team would be:
Top
Mid
Jungle
ADC
Support 
The enemy team requires itself to go all in while Jinx sits in the back nuking everything.Your goal here would be to bait out their hard engages, then use Janna to disengage off of them. However, during all that hard engage, kha jumps into the backline and murders their ADC. Janna forces a disengage, leaving the enemy team in a 4v5 without the ADC, scattered, and without most of their hard engage. Riven and Fizz go in to reengage on the team while Ezreal uses his mobility to avoid the initial engage and then rejoin in to the new engage.
Now, problems with your team are a lack of a true tank and not a lot of CC. However, it's also much better at wrecking someone for being out of position and punishing any engage mistakes. Also, that is a mostly very kitable enemy team (Something that Ez excels at).
Every team has a weakness. :) You basically have three things you need to look at in your team comp.
- What does your team do well?
- How can you minimize the weaknesses your team has in its comp?
- How will it interact with the enemy's team comp?
Obviously, much harder to do in solo que.
A counterpick to Rengar is someone with hard CC and a disengage. Again, he's an all in engage champion.
etc. Also, when laning against him, try to skirt bushes and ward the bush you can't (depending on where you are freezing your lane). I would also suggest playing some of your own games with him and learning his bush engage range to learn how to deal with that.
Does that help?