Similar to showing Magic effects as dispellable for Priests when they talent into Mass Dispel, I think it would be helpful to treat Poisons as dispellable for Shaman who talent into Poison Cleansing Totem.

Added this to line 369 in GridUtils.lua:

dispel.Poison = IsPlayerSpell(383013) -- Poison Cleansing Totem

(I haven't actually confirmed this works just yet, I just looked up the cast spell ID for Poison Cleansing Totem in a log. I assume that's the spell ID to check on for IsPlayerSpell() here).

Try out 2.8.55-beta version

Haven't specifically downloaded your version to test but it's the exact same change I have locally that's working great in keys for me, so seems to be good. Thanks!