Jarvan got the wrong buffs
His damage shouldn't have been buffed. I realize he's a skirmisher like Dr. Mundo, and not a tank like Maokai, but he still has a knockup, a slow, and his trademark ability, his ultimate.
Yeah, sure, damage is all fine and dandy... but then again, Riot buffing damage on juggernauts and tanks rather than... well, tankiness, as well as giving ADC's incredibly easy ways to melt tanks(Lord Dominik's Regards most specifically), has ruined tanks and make every tank either a juggernaut or the champion that carries a Zz'rot portal and protects his ADC during the laning phase, with the occasional lockdown opportunity if he isn't bursted and QSS'd before that.
Now if we were to go to Maokai and buff some of his abilities rather than his damage... well, it wouldn't work out properly. He would still just be Maokai, the useless tank that gets melted and doesn't do much for the team even with his CC and defense ultimate.
But Jarvan is a different champion. Jarvan has a knockup, some base damage, a slow, a shield, generally things to protect him even with the average ADC itemization and he has his ultimate. As of right now, his ultimate's CC use is crap. This game has just too much mobility. Almost anyone can get past his ultimate, even non-dashes like Hecarim's E, simply because his wall is coded like minions.
I think his ultimate should be made like Azir's.
Completely redo it. Recode it, do everything like that to make it an actual WALL instead of minions that can be passed through. And then make it knock back anyone that tries to dash through. This would finally give Jarvan some opportunity. Even if he used his ult and died immediately after, the enemy would still be locked in. As long as the team did something about that by getting out of range of their abilities or autoattacks and then attacked the enemy team from there, the enemy is now down a champion, and sure their own team is down Jarvan but if he jumped on their carry then they're lacking a severe amount of damage.
I think they should lower his damage again to what it was before the buffs, and do this. As of right now his damage is actually a little too insane, being played as a tanky assassin because of the buffs. Not so that he's broken, but his play style is completely changed just out of the blue from a skirmisher to a bursty assassin tanky whatever he is anymore instead of what he was on creation where he locked out a few champions of the enemy team and gave his team a chance to do what they need to do, whether that was Fiddlesticks channel his ultimate into Jarvan's to wipe out the enemy, or his allies taking advantage of it and destroying the others of the enemy team while a few are locked in, and that was perfect until mobility was introduced and Jarvan was destroyed by his lack of useful CC and damage.