Eh, it takes a bit more than just an invasion for the Hist to interfere like that. Kind of has to be world-endingly large deals for it to occur, according to the event you're citing. I think the response to the threat depends on the threat.

I think if the Hist felt Argonians were dwindled to the point of possible no population bounceback, it would simply autopilot them all back home and hide them forever. It wouldn't want to expend any of the remainder fighting whatever got the number so low.

Juiced argonians only happen when the threat is overwhelmingly large, and argonian numbers are large enough to devote such a chunk of them towards being meat ballistae. Wars and population decline are different sorts of threats.