Lumiel was perplexed by Lumiel duplicate's clever tactics. It was very shocking to his part that he was able to execute such a thing. Making him use his head far greater than his imagination. Something he didn't expect in the slightest.
Countering also one of the multi slash's slashes with just a normal eye observation was very heart-aching on Lumiel's part. It was hard to swallow as he felt he was stronger than his current enemy. Or so he thought that it would be a one-sided beating. Facing such an enemy made him think harder about how to kill such one.
Just as he thought that his current job class will be a stalemate, he switched to another job class. Such job class was something he wanted to test, whether it would be enough for his current enemy to be defeated or worst, making the tides against him. It will be a test he was not sure if he can win or not. Well, it would not be confirmed if he will not test it in the first place.