People make too much out of the Argonian assault on Morrowind, really. The Dunmer were essentially fighting a post-apocalyptic war for survival, with no government, no institutions, and no army, after centuries of sectarian in-fighting and House conflict - and
still they stopped the Argonians getting more than halfway into the province. If the Argonians contribute anything to the war on either side, it will be a few belated incursions into Cyrodiil or Elsweyr.
Odahviing is the only one who will fight for u
Lore-wise, that's quite an asset. Dragons have incredible power in lore, not like the easily-slain ones we encounter in-game. One could easily sway a decisive battle, and one decisive battle is all it takes. Odahviing was one of the strongest dragons anyway.