Rather than having random spawns for Nightmare, Storm Bringer, BloodStorm, and ThunderCloud, make them static spawns on Elvia servers, while they are normal spawns on non elvia servers.  To prevent "double dipping" link the health of the 2 so they die at the same time.

To prevent people from "tagging and afking" lock the Upgraded boxes and special drops behind hit totals, if you don't connect with 25 hits for every minute the boss is up (adjust to what makes the most sense) you only get the base version loot.  Making this change however should remove the base version of boxes from the Upgraded boxes, and replace them with +12, +13, +14, and +15 in addition to the Pri, Duo, Tri, and Tet that is currently in the boxes.  Making this change incentivizes people to bring their mains, or at least bring an alt that no only hits the boss constantly, but has at least half way decent gear and is leveled.  There are too many people that bring only sub level 56s that are not even in Oasis gear to the World bosses.

I don't know how it is on EU, but I have only seen Thunder Cloud Kutum die 1 time, most people say they have never seen him die.  Now the rest of the upgraded world bosses all die, but you get a lot of people that just stand around annoyed that the upgraded version spawned in the first place.

Like who would ever go to the normal boss is it would be guarantated awa on the Elvira servers?

This doesn't make any sense.

Fixed number of required hits would not incentivize bringing the main... it would incentivize bringing a ranged alt...

Also (probably) they will increase the spawn rate of awa bosses over the time untill it will be guarantated at a point, as people are more geared in time. (At least this would be the logical thing to do.)

I hope at least some improvements are made to reward those that actively take part and penalise those that don't.

Bringing alts is fine, with how low the DP is on world bosses, even Oasis geared players are able to contribute to the damage.  800 extra ranged characters hitting a world boss constantly would help take it down quicker than when those same 800 players tag the boss 1 time and then AFK in a corner.

I would point out that while it does seem frustrating to have a bunch of players hit the boss once and then sit it out, the fact that they do that improves your chances of getting the good loot pool. And while no one gets fantastic rewards unless they're lucky enough to get a boss weapon or similarly great drop, the players who don't actively participate do get worse rewards than those who do, because they get the worse loot pool. So, while arguably PA should improve the rewards for those who actively participate, it's not necessarily in the best interest of those who do currently actively participate to try to get the rest to do so as well.

But if the goal is to get more players to participate, then they're going to need better rewards and will likely need to get rid of the death penalty at bosses. As long as the death penalty is there, most players will not risk their mains. But the biggest problem arguably is that they made the harder versions of the bosses incredibly brutal while not giving rewards that are all that much better. Fighting them with your main is just begging to lose crystals, and even fighting them with your alts is pretty unpleasant - especially Thundercloud Kutum. Practically no one fights him, because it's suicide, and the special drop they added is absolute junk. An okay-ish alchemy stone that can't even be recharged? How did they ever think that that was a good idea? The difficulty of the bosses is not even vaguely in line with the rewards - at least not when crystals and XP are on the line.

So, I'd love to see better rewards, but I also don't see it as particularly beneficial to try to force players to participate. From what I can see, that mostly makes it worse for the players who do, not better.

While it might seem like suicide, After you learn the Dance with the Nightmare bosses, something you learn by actually participating, they are not as lethal as were originally thought to be.  In oasis, a Witch has no problem at Kzarka, Karanda, or Nouver, and only a slight issue at Kutum because at ~35% health he does an  unavoidable full chamber nuke that 1 hits anyone through block at least up to 430 DP.  The annoying part is that TC Kutum takes the full 30 minutes every time, and the dance against him just gets annoying after the first 10 minutes.  TC Kutum I have tested a Ranger, Archer, Warrior (430 DP yea that was a bad idea), Guardian, Musa (another bad idea), and Witch, of those the Ranger and Archer performed okay, The guardian did slightly better but still got caught constantly, the Musa and Warrior spent more time taking Dirt Naps than they did actually fighting Kutum, I actually gave up on Warrior when I went back to try using 430 DP, the Witch I die like once every 2-3 times now, it's so easy to use Witch that I usually get 30 seconds into the DoT Debuff before I realize I even have the Debuff.

As for the "it's more beneficial to the active players", that is only slightly true, but it also is very very disheartening when you fight the entire 30 minutes Kutum Despawns (NA), and some guy who spent the entire time in the Tunnel gets a TC Box, Belongings of Adventurer, and then says, oh yeah I also pulled 4 1000g bars, while you stare at your 2 100g go bars.