Time to express my views on this.
I. ADORE. The new dragons. It's smart, they have an impact, and if Riot does them correctly this is gonna switch around the meta a fair amount. My prediction? Early game, bot focused meta. I won't be surprised if we circle back to our Season 5 roots and have 5 man ganks bot again, because these dragons are beautiful. You want as many of them as quickly as you can; they stack, last forever, greatly empower you (especially if your - say - a siege team with two earth dragons and one water dragon) and will increase the Elder Dragon buff. But the dragons don't seem like total pushovers, and contesting them's gonna be a big deal; and they're gonna hurt. Water dragon even slows on its auto attacks. The dragons also look amazing. I feel like Earth and Air together will make an incredibly powerful combination; you hurt turrets and epic monsters more and move faster out of combat. Rotating and potentially splitpushing is gonna be a lot better if you have them.
I feel adapting is gonna be huge. Buildpaths included. Not that adapting wasn't big already, but just a lot more. If your a siege comp and the water or earth dragons up next, that's gonna be huge and you NEED that. Get wards, try to time tp's around this. But something else I like is that no dragon is completely useless for any team comp, so your not just denying them getting the buff, you get benefit too. I dislike the random portion, but it's probably the best way. Enforcing an order would be too ridiculous; fire > water > earth > air seems good on paper, but you can just build comps around it and other such things. This forces you to adapt, something Riot clearly likes.
These mage updates are lovable. All of them are good, but a few certainly walk the line. Looking at you, Malzahar. I'm a bit worried about Cass W though. Not the grounded aspect alone; just how large it is. It's the size of the lane, it's gonna be insane. Vel'Koz and Veigar's ult change, along with Malzahar I guess, are literally Riot trying to force out this tank meta and AD itemization (fuck Maw). I'm worried about Vel'Koz though. He does insane damage already, and has true damage on passive as well. Adding this might just make him insane - especially as a support. He's strong early game and now can just melt anybody (which adds to my early game bot focused meta prediction; if Vel'Koz just 2v1's, probably a free dragon). If they fix Syndra's unlimited bugs, with these changes she'll be great. They finally fixed Annie w! Thank the lord. 275% attack speed when Tibbers is enraged, that'll be hilarious to see. I quite like Fiddle's new passive, and sometimes simplicity is best. Veigar's new passive is just going to cement him as a scaling monster. Ziggs w change executing turrets under 25% health just.. scares me. He has to use his escape, so that's great, but it's still very strong.
Rift Herald however complicates things. He never respawns, and is specifically there for splitpushing. I'm honestly not even sure how to feel about this, but strong early game champions that then turn into splitpushers top lane would enjoy this VERY much, since the strength early game helps both their team and them getting Rift sooner denies the enemy team it and helps the top laner so much. While not necessarily strong early game, sure, but a Tryndamere with this will be TERRIFYING. Add in an earth dragon or two, and say goodbye to your base. The removal of Devourer, now replaced by Bloodrazer also means there's going to be less early game farm junglers. 3% of an enemy's maximum health as physical damage is certainly strong if you ask me, but we'll see how it pans out. Guinsoos is now the new sated! Fun. 6 Stacks gives you the sated effect whilst still giving more ap, ad and attack speed in both base stats and per stack.
There might even be more later on, but I've rambled on enough. I adore this new change, and I'm sorry for making you read all that. If you did, thanks. If you didn't, I can't blame you.