The fundamental flaw with Gnar...

There's a million ways you can balance Gnar, but he has one fundamental flaw with Mini Gnar that needs to be addressed. If Riot buffs him in other ways to viable levels, he will have an unhealthy kit. That problem is his safety zone for attacking as Mini Gnar is almost non-existent.

The fundamental problem with Mini Gnar is if you were to play him safely and intelligently, there is almost never a time when it's safe enough to be in attack range (unlike an ADC). Almost every champion in the game if played correctly can zone him because it is too risky to get into range to atack.

And that's why he feeds - his boomerang poke does almost no damage, and no one is going to play him so passively that they never get close enough to do damage, so they eventually get hard engaged upon and don't have the defensive stats to survive.

Fundamentally, Gnar will never work unless his mini-form range, defensive stats, or burst is increased. He just doesn't have the tools to get into range and do damage without being at too high of a risk. I kind of like his small range (it keeps him from being as much of a lane bully), so my vote would be to increase his base health and resistances slightly.