is there any point of moving tempdb files into different disk drive if all LUNs are from the same RAID pool?
There are several potential benefits.


Constraining TempDb Growth
Making disk-level performance counters more informative.
Separating the IO Queues so a log write IO never waits behind TempDB IOs in Windows.
Simplifying storage reconfiguration both in Windows and on the SAN.
Scaling across SAN controllers and enabling per-lun SAN optimizations.