Query tuning help needed (Hash Match and Table Scans)

Question

I need help optimizing the following query (returning ~8k rows):

SELECT A.sys_id, 'AppSvrRels' = CAST(SUBSTRING((SELECT (', ' + T.name)
                                FROM (
                                SELECT A.sys_id, AppSvr.name
                                FROM GTS_DataStage.SN.cmdb_ci_appl A
                                LEFT JOIN GTS_DataStage.SN.cmdb_rel_ci X 
                                    ON A.sys_id = X.parent
                                LEFT JOIN GTS_DataStage.SN.cmdb_ci AppSvr 
                                    ON X.child = AppSvr.sys_id 
                                    AND AppSvr.dv_sys_class_name 
                                      IN ('UNIX Server', 'Windows Server', 
                                      'IBM Mainframe', 'Application Server')
                                WHERE A.dv_sys_class_name = 'Application' 
                                 AND A.dv_u_used_for = 'Production' 
                                 AND A.dv_operational_status = 'Deployed') T
                                WHERE A.sys_id = T.sys_id
                                FOR XML PATH('')), 3, 4000) AS NVARCHAR(4000))
FROM GTS_DataStage.SN.cmdb_ci_appl A
WHERE A.dv_sys_class_name = 'Application' AND A.dv_u_used_for = 'Production' 
    AND A.dv_operational_status = 'Deployed'

These tables are on the DataStage and I am not allowed to use indexes. Total rowcounts are: cmdb_ci_appl: ~20k; cmdb_rel_ci: ~1200k; cmdb_ci: ~800k

The following image shows a section of the execution plan (I can upload the sqlplan file if needed but there's not much else to see):

Any help is appreciated.