Tente algo assim:
ping -n 1 192.168.10.91 > NUL
IF ERRORLEVEL 0 (goto :copyhost1) ELSE goto :skipcopyhost1
:copyhost1
NET USE \192.168.10.91\IPC$
ROBOCOPY 2.168.10.91\lgrdata\ \ICOS\Analyser_backups\LGR_Profile\ /NP /TEE /E /dcopy:T /Z /LOG+:C:\logfiles\LGR\robocopyjob_log.txt
:skipcopyhost1