As always, it's almost impossible to add anything highly useful to such a generic query. What kind of performance issues are you having, and how do you know that you are having them? What tests are you running? What is contained in your user logs?
Possibly because that isn't the problem. As Ipstenu has pointed out, "every server is a snowflake": i.e., every server is unique. Perhaps there is a simple setting on your DH site that is not properly set. It may be something terribly obvious (that happens—sometimes I just forget to release the parking brake) or something buried deep in a php.ini file. Needless to say, no, we are not experiencing ongoing performance issues, but since you didn't indicate what your specific issue is, we are comparing apples to unknown, invisible objects.
I'm not quite sure how "different conflicting suggestions" is "uneven support". I bet your doctor or your auto mechanic tries out different strategies as well. This is typically how problems are resolved—by trying something until you find something that works, and not just for webhosting, but for most fields that I can think of. You start with the easiest, most obvious thing, and work toward those things that are more difficult to implement or obscure.
I wish I could offer you some specific advice, because I host several sites with DreamHost and they all run well. But you haven't given us much to go on, even a link to your site. You seem to have tried some of the standard debugging techniques (disabling plugins, etc.); I have outlined a few more here that you may want to try.