οἱ δὲ Ἀσσύριοι καὶ δὴ ἠριστηκότες ἐξῇσάν τε θρασέως καὶ παρετάττοντο ἐρρωμένως.
is the first kai redundant?
No, καὶ δὴ picks up αριστήσαντες in the previous sentence. They did as he told them.
οἱ δὲ Ἀσσύριοι καὶ δὴ ἠριστηκότες ἐξῇσάν τε θρασέως καὶ παρετάττοντο ἐρρωμένως.
is the first kai redundant?
No, καὶ δὴ picks up αριστήσαντες in the previous sentence. They did as he told them.