I think shadow class need more attention from the dev, they're totally desolate on arena. Ninja and Samurai are useless for the current meta. Magebane can't even bane any mage and assassin keeps getting assassinated first lol.
And i think it's better if you also apply Chaos Knight's swap while dealing damage to Ninja. As for now they need to waste 1st wave to just swap, and can only attack on the 2nd wave (If they're not killed by Talissa Warlock's poison)
Sorry if i'm out-of-topic, but i think shadow class if reworked correctly can be the counter for summoner and archer class.