Mixology makes it so the Flask of the Draconic Mind provides 380 intellect for alchemists, or 399 intellect once you count in the 5% bonus Nethermancy. Nethermancy is also where you see 84 intellect from a Flask of Enhancement, 84 being 105% of 80. Additionally, you can't use the Flask of Enhancement and a Flask of the Draconic Mind at the same time; the Flask of Enhancement exists primarily to give PvPing Alchemists access to their stat bonus.
Note also the part that the guide in general only includes the non-gear bonuses: Much like it does not mention the Alchemist's stone, it also does not mention the goggles engineering can make or the trinkets jewelcrafting can make despite both of those being better benefits than the Alchemy trinket is.
Mixology, combined with [Flask of the Draconic Mind] provides an 80 Int bonus.
The above is incorrect and quoted from the professional assessments in the beginning.
Flask of the Draconic Mind gives a whopping 300 intelligence bonus and can be used by anyone. Aside from being able to more cheaply use this, it is not relevant to alchemy as a skill.
Flask of Enhancement is the correct flask, and alone would provide an 80 bonus. Mixology further increases that.
Also if you equip the Vibrant Alchemist Stone, you will gain 301 intelligence. That trinket equipped with a red gem gives another +10 int socket bonus, and of course another possible 40 int if you chose to gem with int.
Possible professional increases of intelligence through alchemy far exceed an 80 bonus.