So, we played 3 games, and Ossir won 2, while Letos won 1, thanks to the Morale of Dragons!! I don't even consider Ossir's luck; it's his skill.
As I said, the chances of Letos winning against Ossir are no more than 50%.
But in general, if Letos casts a spell, Ossir dies with an 80% probability (even with luck).
However, if the first cast is reflected or immediately removed by Ossir before the turn of the archers and knights, it's already a 50% chance of losing, and if one more of the subsequent casts is reflected, it's a complete loss for Letos.
P.S. Of course, the opponent's gameplay is excellent (it's clear that they've played a lot), so these are the numbers we get, but in general, I still believe that among the non-imba heroes, Letos is one of the most dangerous for Ossir