Combine Table Hints INDEX and FORCESEEK with Two Joins Not On PK
I would also test this rewriting (aasuming that sID is the primary key of docSVsys):

SELECT COUNT(*)              
FROM [docSVsys] AS d
WHERE EXISTS
      ( SELECT * 
        FROM [docSVtext] AS sv
        WHERE sv.[sID] = d.[sID] 
          AND sv.[value] = 'doug'
      )
   OR EXISTS
      ( SELECT * 
        FROM [docMVtext] AS mv
        WHERE mv.[sID] = d.[sID] 
          AND mv.[value] = 'doug'
      ) ;