That answers the question if there can be a tie, what was asked in another thread, with "no".
Probably your last champ died from damage reflection, but your damage was dealt first, so you are declared as winner.
/edit: Warden has a damage reflection skill, fits perfect into the theory above.
Ceterum censeo, the ban of my main account should be undone, I didn't spam, the detection algorithm doesn't work.
Actually, Ignatius died from damage reflection.
In the 2nd turn I used Madame Serris A2 skill and therefore she stole one of the damage reflection debuffs. After Serris turn Elhain nuked everybody with her A2 except for Ignatius. Therefore, I thought, I failed to beat the enemy. As expected Ignatius used his AoE attack and killed all my champions and himself. Only then I realised that Serris stole a damage reflection debuff.
I always thought that in such a case I would loose. Reason behind my thinking was that if I am unable to beat the enemy as attacker and the defender gets his/her chance to strike back the defender is the winner. In this case it seems to be that Ignatius, which was badly injured has died before my champions died.