Overall looks really good. But Ravage Agent says it triggers when "a model activates" - does that mean that a squad of 10 activating near a ravage marker will immediately trigger the ravage agent 10 times? (And is probably wiped out?)
And does the growth at the start of the next turn happen "once, if it killed something" or "once for each thing killed". Because the combination of those two seems like it would very rapidly devour everything if something strays too near.
Or was it meant to be "when a unit activates" and only kill one member of the squad, before growing next round?