I've observed that Alchemy is best for primary skills and that it works in cool ways.
Obviously if you have the highest of either the HP or MP, you will take more Dmg but in PvE, that's not too bad as HP isn't a big deal in high floors.
Alchemy does increase DMG by 50% of current MP and/or HP% of course but that's if you have the lowest of either MP or HP when recovering.
If you don't have enough MP for a skill, it uses HP to cast a skill. Another thing is that it's great with Masochism or Hunger.
Of course it's not best for special skills , even with Masochism or Hunger as special skill have larger cost which can make it drain faster and it's harder to cast consistently. There are better mythics for special skills of course but I could only find this mythic for Primary skill casting other than Energy (Energy best for high attack speed primary skill).
If I use HP on hit and HP Regen, the skills use MP. If I use MP regen/MP on hit, it uses HP to cast. If I run out of MP, the Alchemy Mythic prioritizes HP for casting and vice versa. A vice versa Mythic indeed.
At least it's easier to cast with primary skills and a huge boost of damage, great with high recovery of the resource by on hit effects and Masochism or Hunger.
The fairy does heal HP but it has capabilities to heal MP as well with alchemy which is also nice.
The reason why I post this is because Alchemy seems hardly explored but looks like a great mythic with its potential. I plan on making a good primary skill build.
Griffin already made one before but with Wand and Energy mythic. Any primary skill that's viable can definitely be used very well with alchemy and something to combo with it.
I plan on making a primary skill based build with this concept. One thing I can definitely agree on though is that it should NOT be used for PvP.
Lastly, there has not been an Alchemy build in the forum's before as far as I know. The mythic can be tricky kind of to control but once you control it, it's a great mythic in my opinion for a primary skill build that is very good at high floor clearing which I can definitely see. Also I out Masochism or Hunger to keep the values of HP and MP at around 50% for the alchemy to work better . Totally optional though. Equality could work with it too .
I'm curious to see your input on Alchemy Mythic. I kind of like it and dislike it but I'm giving it a shot anyways. I know I could use energy mythic for primary skill build but I want to be unique and energy for some isn't the best as it take more slot and APS to be as sustainable with the 10% energy per primary cast and 30% recovered energy.