I'm not sure what we are talking about when we say stacking, do we mean you get the stats from the buff or do we talk about being able to have both buffs up at the same time?
For example MotW didn't stack with resistance auras in retail but it isn't replaced, you only loose the motw resistance effect when you get a resistance aura/totem.
If I recall correctly we had some kind of source saying armor pot not giving any extra armor while having stoneshield pot active and due to the limited stacking system VG decided to run with we could only replace buffs and not remove the effect/parts of the effect from it. Same goes with Brute force where we had to decide if it should be replaced by a stam buff or a str buff.
I'm also pretty sure (was over 4+ years ago I bothered with stuff like this) there was/is a video of someone with both mongoose and agi potion up at the same time, doesn't mean you get 25 + 25 agi but he had agi potion on trash and used the mongoose one for the boss just for the 2 extra crit.
@sam yes bosses on VG are buffed in most of the cases, for example PW does hit every 0,7 sec instead of every 1,5 sec. His HS can also hit the MT which it cant on that server. Gluth has been downed before 1 decimate on VG, I think it was back when you had unlimited debuffs but ppl only had loot from 2 wings available and and that was without DM/event buffs.
tdlr 2 buffs at the same time doesn't mean you get both effects, VG is overtuned and dual wield wont work in all fights. It's rare to fill a raid with 40 good players on VG due to the server population but getting Gluth and Anub down like that should be doable on VG.
1) Is this legit server script, that you could tank end game content aka Naxx bosses as dual wield fury/prot spec?