<Page> Exhibit 99.11(a) SULLIVAN & WORCESTER LLP 1666 K STREET, N.W. WASHINGTON, D.C. 20006 TELEPHONE: 202-775-1200 FACSIMILE: 202-293-2275 1290 AVENUE OF THE AMERICAS ONE POST OFFICE SQUARE 29th FLOOR BOSTON, MASSACHUSETTS 02109 NEW YORK, NEW YORK 10104 TELEPHONE: 617-338-2800 TELEPHONE: 212-660-3000 FACSIMILE: 617-338-2880 FACSIMILE: 212-660-3001 September 18, 2003 Touchstone Variable Series Trust 221 East Fourth Street Suite 300 Cincinnati, Ohio 45202 Ladies and Gentlemen: We have been requested by Touchstone Variable Series Trust, a Massachusetts business trust with transferable shares (the "Trust") established under an Agreement and Declaration of Trust dated February 7, 1994, as amended (the "Declaration"), for our opinion with respect to certain matters relating to the Touchstone Enhanced Dividend 30 Fund (currently known as Touchstone Enhanced 30 Fund) (the "Acquiring Fund"), a series of the Trust. We understand that the Trust is about to file an amendment to its Registration Statement on Form N-14 (File No. 333-108157) for the purpose of registering shares of the Trust under the Securities Act of 1933, as amended (the "1933 Act"), in connection with the proposed acquisition by the Acquiring Fund of all of the assets of Separate Account Ten of Integrity Life Insurance Company (the "Acquired Account"), in exchange solely for shares of the Acquiring Fund and the assumption by the Acquiring Fund of the liabilities of the Acquired Account pursuant to an Agreement and Plan of Reorganization, the form of which is included in the Form N-14 Registration Statement (the "Plan"). We have, as special counsel, participated in various business and other proceedings relating to the Trust. We have examined copies, either certified or otherwise proved to be genuine to our satisfaction, of the Trust's Declaration and By-Laws, and other documents relating to its organization, operation, and proposed operation, including the proposed Plan, and <Page> 2 we have made such other investigations as, in our judgment, are necessary or appropriate to enable us to render the opinion expressed below. Based upon the foregoing, and assuming the approval by contractowners of the Acquired Account of certain matters scheduled for their consideration at meetings presently anticipated to be held on December 5, 2003 it is our opinion that the shares of the Acquiring Fund currently being registered, when issued in accordance with the Plan and the Trust's Declaration and By-Laws, will be legally issued, fully paid and non-assessable by the Trust, subject to compliance with the 1933 Act, the Investment Company Act of 1940, as amended, and applicable state laws regulating the offer and sale of securities. We note, however, that under certain circumstances, shareholders of the Trust may be held personally liable for its obligations. We hereby consent to the filing of this opinion with and as a part of the Registration Statement on Form N-14. In giving such consent, we do not thereby admit that we come within the category of persons whose consent is required under Section 7 of the 1933 Act or the rules and regulations promulgated thereunder. Very truly yours, /s/SULLIVAN & WORCESTER LLP --------------------------- SULLIVAN & WORCESTER LLP