That's exactly what happened, but regarding the chances – it's debatable.
1. Your army probably wouldn't be able to kill my ballista, and once you were left without archers and druids, it would be easier to finish you off, even despite the large amount of mana. (I'm not sure if Vengeance works on the ballista, though?)
2. It probably wouldn't be a very pleasant surprise for you to see +2 speed for all my troops (home territory), and for the cavalry, that's also +20% damage, and the dryads would hardly stand in the way...
And the fact that 3 stacks of flies, knives, and horses fell – that's nothing.