Is the upper limit of 60000? 
With out epiphany yes 
With epiphany though, the cap of both mp and hp regen is 37,500. With epiphany, the total mp and hp regen you can get is 75,000 (37,500 ×2). That means with druidic, if you filled both of them, your poison cloud would be at least 18 times stronger with poison dot.
（30000+30000）/4000=15 times
what’s the poison dot？BLIGHT？ 
（30000+30000）/4000=15 times what’s the poison dot？BLIGHT？
Poison dot is just the dot default. Toxic makes the dot deal 400% of damage. Poison deals 80% dmg in 8 seconds and toxic elemental critical makes you deal 400% of 10% each second. 100% blight for example makes the toxic deal 100% of the 400% dmg. This makes toxic deal 800% of 10% dot dmg per second for 8 seconds. If I had 600% blight though, toxic would deal 3500% of 10% dot dmg per second for 8 seconds.
The dot gets 15 times stronger so dmg dealt by poison dot is X15 each second and elemental crits just make the dot even stronger as a poison cloud. Furthermore the plagued set affix multiples the poison cloud dmg by 125% per enemy and with these crits, you can imagine how stronger this becomes. A very powerful multiplying build has very large % values of multiplying and high numbers too.
If it was ×15 to make poison dot stronger, percentage wise, it is 1500% stronger. With epiphany, you deal even more potent dmg, at least up to X18 more dmg to be that much stronger. From this perspective, I can already tell it looks stronger than a frozen build such as hachimon. Green garden was broken at prior to its release because of the poison cloud self replicating on itself so much and as if the poison cloud wasn’t already so powerful, the clour exponentially grew. Thie can be replicated today with coat proc or skill actually but it might be fixed so it doesn’t do it anymore.