Yes, they act as a decoy or hitting targets for your aros so instead of fighting against eachother, these tankmates distract their attention. another way is to get your aros well fed. this will also reduce aggression between them.
I tried an aro community -but to make a long story short -now I have no aros .Maybe w/ a huge tank and more then three might be successful tho .Ive certainly seen lots of pics w/ multi aro tanks -but not something Id personally try again.