No root needed, just install Boldbeast Recorder and go, HTC One E8 dual sim can record calls perfectly in two sides.
There is a bug in the HTC One E8 ROM of Android 4.4.2 - Sometimes when the call is hung up the ROM doesn't notify the app. We found this bug in the ROM of HTC Desire 820 Android 4.4.4 also.
If you are using other recorders you'll see "the call is hung up but the recorder continues recording".
However Boldbeast Recorder can bypass the bug and detect the call state correctly, therefore works far more good and stable than other recorders.