Anything short of the removal of world buffs, and a 50% hp buff (at minimum) to all bosses, and Kronos Naxx will be disappointingly easy. I've already provided plenty of evidence and analysis for why, but if you need a recap, here you go:
1) Vanilla Naxx was tuned with a specific number for raid dps in mind. Every PTR, Blizzard observes raid dps very carefully--often using volunteer top guilds to do dps benchmarking work (I participated in several), in order for their devs to gauge how to set boss timers, hp values, etc. Raid dps was observed prior to Naxx in Vanilla, and boss hp values were set accordingly to challenge the top guilds of that era.
2) 2017 overall raid dps is much higher than it was in 2006, even comparing an average Kronos guild to the top retail guilds. We bring fewer healers, we bring fewer tanks, and we optimize gear, buffs, and debuffs much better. All those equate to higher raid dps. How higher is our dps? Using data from kill times from 2006 Naxx, and comparing those to the kill times of the average Kronos guild clearing AQ40 regularly, without world buffs, we are doing 75% - 100% more raid dps, on average. That's excluding guilds like Onslaught, Synced, and Vanguard, who are even higher...
3) Higher average raid dps means bosses die much faster than back in 2006, which means significant boss mechanics and even entire phases can be completely ignored or skipped. Noth wasn't designed to be killed before his first balcony phase. Heigan wasn't designed to be killed in only one, or even zero dance phases. Patchwerk wasn't designed to be killed in only 3-4 minutes the first time your guild sees him.
Doing roughly twice as much dps as guilds did back in 2006 means that we are basically required to execute each main boss mechanic ONCE (if at all), and then the fight is over. Back then it was 2-3 times. Obviously, the more opportunities you have to fuck something up, the better chance someone fucks it up. That's what made Naxx difficult. Most of the fights were unforgiving. One death would snowball into more deaths, and soon you were falling behind. But because of our high raid dps, that won't be the case here on Kronos. Your Zombie kiters fucked up on Gluth and died, and you barely got through the first Decimate? Who cares, since the boss is already at 10%! 12 people died to the first Polarity Shift on Thaddius? Who cares, because you'll still kill it 2 minutes before the Berserk! Only 30 people showed up for your Patchwerk progression raid? No problem, you still can kill it well before the Berserk timer!
If you think an un-buffed Naxx is going to be hard, even without world buffs, you need to stop fooling yourself. Elysium chose to leave everything Blizzlike. Want to know how hard their Naxx is? Some guild named Scuba Cops (never heard of them) went on their PTR, and one-shot Kel'thuzad--the final boss in Naxx, and arguably the toughest encounter in all of Vanilla. Does that sound like fun to you?
So no, I don't want Naxx to be so hard that even the Synceds or Vanguards of the world take two months to clear it, like back in 2006, but I do want it to live up to the hype, and the expectation that Naxx will be a challenge, and it will all be worth the two years of waiting that we've endured. If the staff wants to implement some sort of regressive system where hp is lowered over time until we reach blizzlike values, then fine, but please, I implore you staff members to do your best to give us a Blizzlike progression experience, and not another LFR raid like AQ40 was, and like Naxx will be for all those poor Elysium suckers. This is your chance to do something different than them--and to give the community a challenging, and fun Naxx--an experience that players will remember for how enjoyable it was, rather than for how disappointing it ended up being!
-No world buffs (can be brought back later at some point)
-Buff boss hp 50-100% depending on boss (I would be happy to give suggestions)
-No "invisible" changes or timer changes--buffing hp is easier and accomplishes the same goal
That's all we need.