It is doubtful than an attorney can do anything to move your case along any faster. As long as your investigator is still with the EEOC and contacts you periodically, you know the agency is continuing to work on your case.
EEOC investigators carry a huge workload of cases. Much of the investigation consists of waiting, they call the employer or employee and wait for a return call; they request documents and wait to get them; they request a witness list from the employee and wait for that information; they call the witnesses and wait for a call back; if one side offers a settlement, they call the other side and wait for a response. The job of EEOC investigator is not easy, especially when balancing the number of cases they do.
Your case may be helped by the introduction of an attorney who will work with the investigator, especially if the investigator has been asking you for information that you have been unable to provide, if mediation has been scheduled, or if the employer is willing to enter into a settlement negotiation. On the other hand, an attorney who merely calls the investigator frequently just to ask when the investigation will be finished will hinder the completion of the case, in addition to costing you attorney fees.
The most helpful time to get an attorney involved in an EEOC discrimination case is before you file your complaint with EEOC. An attorney can review the facts of your case and may be able to find additional claims that need to be filed. The attorney can also draft the legal brief and file the complaint with the EEOC. Then the investigator will begin the process by working with this attorney.