A new question here. With the rule of one it seems useless having more than one slann on the table, doesnt it? They have 3 spells each but they are the same, so they couldnt repeat them. Same with slann+kroak, because they share the two basic spells and couldnt use their full 3/4 spell
Basically. The only benefit could be trying to cast if you failed the spell with the other. You will also get two constellations.
Nope you can't retry if you failed the spell. Rule of One disallows attempting a spell more than once per army. Otherwise it wouldn't be so bad IMO.
Who knows? maybe in the future we'll have a battalion with 2 slanns. Actually, it makes no sense to field 2 of them.