That sounds suspiciously like the IO Controller threads - especially the disk task - was getting clipped by the OS. You may think that is weak, but we had a huge issue with Solaris customers moving to the threaded kernel due to an OS bug that prevented process threads from doing kernel async IO. Oracle released a jumbo patch to fix and then we had to put a config in sp50 & sp100 to enable. With saying only 2 threads/core, however, I don't suspect you are running Solaris on SPARC.... What is your OS release??
WRT solved cases - sorry - I can't address that - that is a question for AGS support.