Aside from pathing issues, what was better scripted on Nostalrius?
First off, I hope the admins don't take this post as Kronos-bashing and instead as constructive criticism.
I think you're greatly underestimating how important pathing is.
Broodlord/techs coming through the ceiling in Vael's room - that never happened on Nost.
Hatchers practically do no damage in suppression room. You don't even have to have pummel/cs/kick keybound. You could pull multiple at a time because the damage aura ticks for 50.
If you step on the railing in BWL on Kronos, you pull the entire instance.
If you have a pet active in BWL past Firemaw it could, for no reason at all, run and pull the whole instance.
I'm sure you've all encountered the problem on Ebonroc/Firemaw/Flamegor where they straight up don't use Wing Buffet.
The Chromaggus encounter is completely negated by the tank LoSing the breath. (he also hits like a bitch)
Just last week, Chromaggus got stuck in the ceiling for 5-10 minutes.
Nefarian randomly walks toward/faces the raid even when he has the tank targeted (Alliance probably doesn't have this issue)
And this was only from July onward, when Kronos had been out for over a year. None of these problems existed on Nost.
Now about tuning. Obviously on Kronos there's 1.12.1 dungeon gear and titanic leggings, earthstrike, etc, which make the raids easier by default. Bosses also hit for less on Kronos. King Gordok on Nostalrius hit harder than Nefarian on Kronos.
As for Molten Core, there's the Shazzrah blink "you must be facing your target" bug, Ragnaros threat bug where he just slams whoever he wants.
Moreover, (almost) anything that has a chance to proc on Kronos procs way more than it should. Mace stun, frostbite, impact, Ironfoe, blackout, imp concussive shot, etc.
Engineering on Kronos feels like a waste of gold, with the exception of reflectors. With heartbeat resists being as fucked as they are, you're not likely to get out of the Rocket Helm knockdown before your target breaks out of the cc.
Warlock pets are laughable as well, all having the wrong skills and whatnot.
As for class specific bugs:
Warrior: Might as well remove charge from your bars. 100 rage executes being dodged and taking all your rage, whirlwind not proccing shit (although this may have been fixed). Intercepting C'thun and ending up in the room before Bug Trio, lying on the floor dead as fuck. Intimidating shout breaking in 3 seconds.
Hunter: Feign Death being resisted more than 50% of the time, tranquilizing shot resisting.
Warlock: Pet pathing in Warsong Gulch, seduce not working.
Priests: Psychic Scream undispellable.
Mage: Slow debuff priority. For example, using Cone of Cold on a target affected by Improved Blizzard. The target retains the Improved Blizzard slow, Cone of Cold doesn't apply a slow and only does damage. Cone of Colding a rogue right after they vanish also won't apply a slow, this is similar to the rogue Improved Sprint bug.
Rogue: Improved Sprint gives a 1~ sec immunity to slows. Vanish stinks.
This is just off the top of my head. Of course Nostalrius wasn't perfect, but the circlejerk I see on the Kronos forums is UNREAL. I'd suggest doing what Dervin said and, instead of acting like Kronos is the best scripted server in pserver existence, take a good hard look at Kronos. If Kronos was seriously scripted so much better than Nostarlius, there would be no fear of a mass exodus. At this point, (most of) my guild and I have spent more time on Kronos than Nostalrius, and they're more than willing to drop the past 7 months of work to go back to Nostalrius.