X2 SONAR Studio comes with the "SI-Drum Kit" which is the new name for "Studio Instruments Drummer". If you follow the instructions in the video in the thread above
http://forum.cakewalk.com/fb.ashx?m=2802474 (nice vid Charlie) and you do not see the MIDI patterns in "SI-Drum Kit" pattern browser, you might want to try an advanced install of X2 and resintall the "SI-Drum Kit". FYI, the "SI-Drum Kit" MIDI patterns are physically located in a hidden directory C:\ProgramData, the full path to the pattern directories is "c:\ProgramData\Cakewalk\Studio Instruments\SI-Drum Kit\Patterns".
You should still be able to use the methods you were using in MC5 updated to the X2 interface. If you wish to incorporate the step sequencer into your workflow, do so. You can edit the MIDI clips in the PRV or step sequencer, whatever works best for you.