Some of this may depend on how much data is actually in SRMARRAYDEVICE.SHAREDOBJECTLIST. If many of the rows have lots of data in this field, then the formula itself may not be the issue, but pulling the data in from the database could be taking a long time as well as rendering this field in the report.
Also, I might rewrite the formula a bit (but I'm not sure this will help with the speed...)
if "Orphan" in {@Get current hostorhba} then
if clustergroup <> "" then
uppercase({@Get current hostorhba}) + " Possible Host(s) = " + clustergroup
else if not(isnull({SRMARRAYDEVICE.SHAREDOBJECTLIST})) then
uppercase( current hostorhba}) + " Possible Host(s) "
+ {SRMARRAYDEVICE.SHAREDOBJECTLIST}
else ({@Get current hostorhba})
-Dell