Seijuani is grossly OP
Cinderhulk allows her to straight up 100-0 squishes with little effort or counter play, and if she gets a kill or two early she becomes unstoppable for the rest of the game because she's a tank - once a tank gets ahead they'll stay ahead as long as they don't do anything retarded and go about things practically. Tanks come with little risk, I can't punish an out of position Tank like how I can punish an out of position Lee/Kha/Vi, tanks also always have their CC to fall back on, so they'll always be useful, even when behind. Further more tanks can go on any target they like, unlike Carry junglers who have to aim for specific targets. I'm honestly hating this Cinderhulk thing, it just seems OTT really. I get that Tank Junglers need to have their place, cool, but I don't believe that they should ever allowed to dominate the jungle, nor do I believe that a Tank jungler should be allowed to be effective in every situation. That's just overkill. Cinderhulk meta = Tank gets a couple kills early - proceeds to gain control of their jungle and AFK farm, then shows up to dominate every Objective contest or TF with little effort. May occasional decide to waltz around your own jungle once they get cocky.
I can see you outdueling you any time. Rengar does really well agaist squishy but mostly because his bruise is insane, he is not the most durable champion specially since you had no life steal. Armor pen does ticklish to sejuani early as they will normally get HP first, flat AD would have work better but then again on rengar you want the armor pen. As for the dragons, let me tell you that early dragon is worth 4-5 extra AD so is not really worth mentioning a drake in here.

THE FRELJORD IS MINE!!!!!