A few thoughts: Why are you concerned about locking of the temp tables, they're only accessible from your own session.

Furthermore, option maxdop 8 does allow for parallelism yes, but it is generally not recommended to span NUMA nodes, which maxdop 8 may do on dual quad servers. I do think maxdop 8 can potentially cause more performance issues than maxdop 4 in some cases, and this SHOULD be configured correectly as a server option by the dba.