There are 2 files in the /system/etc directory (powerdaemon.xml and powerdaemon_z3.xml) that are used to monitor various states of the system (ie. "booting", "games", "video playback"). Certain constraints are set depending on the system state. Most of these constraints are a variation of the "ondemand" or "performance" governors. These constraints adjust the min/max frequency and set control to a specific governor. This is why you can not get any cpu governor settings to stick.
What I changed:
I changed all system states to be directed to the "normal" constraint. This constraint does NOT change the selected governor and has min/max frequencies of 0/150%. This basically disables any effect the powerdaemon has. The 150% max does not mean your cpu will run at 150%, it simply allows overclocking if your kernel supports it.
In my testing, simply deleting the files or disabling the system states caused higher than normal cpu usage. It seemed to be trying to continually process information that it couldn't find. So, creating a "normal" constraint that did not limit any funtionality seemed to be the best option. The powerdaemon controller still processes everything, but has no real affect.
Download and flash the Powerdaemon.disable.zip (with custom recovery). You may want to make a copy of your original files if you are using a different model.
If you want to restore the original xmls, just flash the Powerdaemon.restore.zip. These are from my T210R.
Flash at you own risk. I tried my best to explain what the mod does, so I take no responsibility for what you do with your Tab.