Beginning to think OP was right all along, the totems are taking AOE impact damage which makes it unlike any other AOE in the game. I cant think of a single AOE other than this one that kill totems.
Proof from logs:
|00:08:05.444|Environment Toxic Spores Mana Spring Totem V 5 5 (O: 2977)|
|00:08:05.479|Environment Toxic Spores Grounding Totem 9 5 (O: 3149)|
That’s the spell-ID for the impact damage only.
Impossible that both of them were targeted by the spore so at least one of those totems took impact AOE damage. Totems are NOT supposed to be killed by any ground based AOE. This looks like a bug.