Difficulty of end-game PvE content?

[Crinos]

Greetings.
I'm curious about difficulty level of end-game PvE content.
My plan is to level up my warlock and focus on raiding just like I did on retail

Are dungeons and raid(s) tuned like they were in vanilla difficulty and script-wise?
What about BWL and other future raids bosses - will they be exact same like they were in retail vanilla with all their little bugs and randomness?
Or some special changes will be made in scripts, boss abilities etc. to make them less of a mess in some cases?

Why I am asking - some bosses (esp. last of AQ40 and some of Naxx) were strangely tuned by Blizz (and they admitted it that in some cases fights were really overtuned).
I'm just curious if there will be any custom "fixes" to make some bosses less of a mess and more "clean" so players can focus on fighting boss, not random bugs. Or maybe everything will be released and left as-they-were?

[Bioness]

So far there are no custom fixes and the scripts are near identical to how they were in Vanilla.

Having said that, vanilla raids are not hard. People who claim they were/are don't realize how horrible players actually were back in 2006, even the hardcore raiding guilds were mostly terrible. If Nostalrius were to make custom changes, I doubt they wouldn't go further than simply increasing the boss health pool (kinda like Feenix, but not so terrible about it).

As for bugs relating to bosses, if it were something that later got fixed, it will be fixed here.