It's no secret that Gnar Is kind of struggling in solo Q. We know that u r careful with him so he doesn't become a pick or ban champ in pro play.
I suggest increasing his health growth from 65 to 80/85. I know he should be squishy in mini form, but he has 300-400 less HP at level 18 than most of squishy carries. HIs base HP at level 18 is so low at 1610 while most of squishy champs r usually sitting at 1900-2100 HP.