In answer to your question, no. Rear speakers, traditionally know as ‘surrounds’, carry a completely separate signal, and adding them would have no effect on the center channel of the Arc. 

I have never been a fan of ‘The Batman’, even in the theater, for exactly the reason you’re experiencing. I thought it was poorly mixed. You may want to try another movie as your ‘test’. 

Hi Airgetlam,

I appreciate your response. I have watched other movies and have been pleased. Glad someone else noticed that about The Batman. I guess my thought process was, if the surround speakers take some of the audio away from the soundbar then maybe the soundbar itself can pronounce itself more.

I would imagine adding surrounds would help a little as the front soundstage will be less cluttered with the combined audio channels. But don’t expect a dramatic improvement.

However, that shouldn’t affect the center (dialog) channel, just the right and left. And I suspect 90% of that is more psychological than not. 

Just enable subtitles for movies starring ‘Mumbleman’.