Yes, I agree that Corrosive Orchid is good in a vacuum. It could be very good (but not broken), for example if there was a card like...
"Renewing Rain"
16 mana, full action, range infinity symbol, Nature Level 4 incantation (crucially no Hydro subtype)
For each of your Plant conjurations in the arena, you may remove it from play then return it to play in that same zone and attached to any object it was previously attached to.
This removes all damage and conditions (like burn) and resets these flowers with Mist tokens, not broken as it's only Plant conjurations. The "may" is because in some cases it will be worse off e.g. mana accumulated on spawnpoints. Magic players will be very familiar with "flicker" effects - leveraging coming-into-play effects is a blue/white strength (my favoruite colours). Here we have a very expensive (>1 turn of mana), uncommon (4 spell points investment), action-intensive (full action) but powerful effect if you build around it to leverage potency.
The fact Mist tokens appear in 2 cards so far indicates there'll probably be a mechanic to refresh. If so, this makes level 3 Lotus good and Level 2 Orchid very good (lower level as Druid has access to Corrode, Dissolve is 1 spell point whilst Sleep is a new frontier for Nature).
If there is a refresh mechanic for Mist tokens, then I offer an apology, Aaron, for slating Nightshade Lotus. Cards in a vacuum eh?