dtrace does not work on Redhat - try systemtap.
https://sourceware.org/systemtap/wiki/HomePage
That is a good tool. It requires some learning, and is able to probe directly into processes and driver information. However, that is what some existing tools do for you now.
But before you abandon iostat do not sell it short - iostat does provide good information.
You need to exploit some of the options.
sar -d (requires sa to be turned on, usually via crontab) does show great information.
vmstat -d does something similar. Very useful.
So, now that you see there are lots of tools, please show us a sample of your iostat output and your iostat command.
