Are you speaking about Tornado ? I don't think it is really powerful (but I might be wrong indeed). I think the consensus is that it is not that much for a Tier 9.
Actually not, I was thinking about your version of Entropy : because of auto-hit and duration (12s base!), you are able to One-Shot everyone including Dorudugan. You only need Mohora Tanga, or Effort, good Per (enought for at less always hit) and Avenging Storm or Boltcatcher. You dont need swift flurry for that. 😁 (I didnt mention it in the related topic to not ruin the Entropy's BPM users 's experience).
About Tornado, I suggest to you somethink that can make sens : the Vertical Launch duration (here :0) can be made in function to the height of the effect. (Mule kick 7m, 1.5s ; Skyward kick 10m, 1.5s (>>2.2s) ; Launching kick 10m, 0s (>>2.2s) ; Tornado 15m, 0s (>>3.3s)) Entre Parenthèses some value scaling with int that take into account the height on the Mule Kick model (/4.5). But that can also climb by spell's level.
Maybe, instead of a Similar Classes comparison (3 spellcasters, 2 spell-regen, 3 martial offensives, 2 martial support/tank) another question can be posed :
"is Maelstrom above the curve of Druid power?" I mean, Pollen Patch can be increased to env. 20 heal/sec/patch (staying immobile count for 1 patch) for the whole party for an extendable duration. (PP and Entropy (unmodded, because as you said, knowledge is power) are my favorite and most used spells with my druid).
Touch of Death destroy any Near Death vs will, in addition to Constitution debuffs from Venombloom or Plague of Insect (-25% base health) a boss fight can be quickly done. Speaking about megabosses, that can be more significant than Maelstrom.
Druid's Insect DoT spell at tiers 9 could be, in the spirit of the curve, an empowered version of Plague of Insect with a good natality for them, so like Toxic Strike in AoE (scaling with Beast and Rejuvenation KW) ; or a spell version of the IRL locust cloud, I dont know. In the fact, the tiers 9 spells that are unpowered for a druid are summons, but all the curve is low, and Tornado (Tornado seems to shine for the 15m launch in the code, but that have no effect so..).
But that is only my opinion, yours is not less valuable even for me!