by Youfie » Sat Apr 11, 2015 7:57 pm
Basically, Elixirs that give +Stat don't stack with class buffs that give +X to that same stat. Only the highest is applied to your character, even though you might see both of them on your character buff list.
This means Elixir of the Sages doesn't stack with Priest's Spirit buff, Elixir of Intellect doesn't with Mage's +Int, +spirit Crystal from Un'Goro buff doesn't stack with Priest Spirit, etc.
Elixir that have +X to the same stat don't stack with each other either.
The Elixir that grants Strength & Stam has its stam nullified by the priest Stam buff being higher, and his +Str component is also useless if you use the Elixir of Giants (higher +Str, no stack).
This also means Mongoose & +Agility elixir don't Stack. Superior Arcane Elixir doesn't stack with the regular Arcane Elixir.
Scrolls don't stack with class buffs, you're supposed to have an error message stating "a more powerful spell is already active" (not in the cases above).
+Str Juju doesn't Stack with Elixir of Giants, nor does the +AP one with Winterfall Firewater or the +int one with Mage Intellect.
+25 Buffs from Blasted Lands stack with everything, and so do the +50 Stam / Spirit buff from ZG (and, of course, Flasks).
Regarding foods, you can only have one "Well Fed" buff on you, and only one "Alcool" (e.g. +Stam Rhum).
Can't remember exactly regarding food that give +Stat (e.g. +10 Int from DM, +Stam from Felwood or +Agi from regular cooking) without actually being Well Fed buffs, I *think* I remember researched carried out during beta showed they were sorta merged with Well Fed buffs by Blizzard at some point during Vanilla even though they didn't actually had the same name, and thus didn't stck with them.