I think it's worth changing the elimination rule partially or completely.
Each of the two duelists eliminates 1 Castle out of 6 possible (the non-host goes first). From the remaining 4 Castles, the host chooses the first Castle, and then the second player.
The point is that the Host has an advantage:
1 (non-host) eliminates - this is normal
2 The second player, after thinking, will come to the following conclusion. Since he chooses first from the 5 remaining, he will not eliminate the race that he needs and will most likely choose the strongest one, and therefore eliminate the next race after the strong one from the 5.
As a result, the host has a choice of 5 races, and the "non-host" has a choice of 3, and I think not the best ones.
P.S. Maybe just make it like in the World Championship. Eliminate down to 1 race, or random with a restart.
No, everything is fine. Considering that there are no однозначно strong and weak races, the "non-host" has compensation, the advantage is in being able to choose a suitable race to match the opponent's already chosen race. For example, you are the "non-host" and eliminate Chaos. The host eliminates a strong Order and chooses, say, Death. Now you, as the "non-host", can choose a good counter - Life, which is very effective against Death, or Nature (perhaps it's not worth choosing Barbarians, as a single Vampire touch is worth a lot). So it's not that bad.