The Incredible 2 cannot be rooted from 2.3.4 Gingerbread, however from 2.3.3 it can. The first step is to take your Incredible back to a 2.3.3. OS.
Roll it back
This can be accomplished through a tool called Downgrade VivoW with hboot .98. I don’t have any idea what all that means, but the package contains ADB, fastboot, and the OS files you need in order to downgrade. You will also need to have particular HTC drivers installed on your computer. The link to the original post on XDA forums is here: [Tool] Downgrade VivoW with hboot 0.98 - xda-developers
Prepare your computer
It’s really important to quit, turn off, or disable all phone, mp3, or pda syncing software including iTunes and HTC sync, antivirus software, and any extra processes that you don’t need so that Windows doesn’t interfere with installation.
Install HTC usb drivers
Pretty much self explanatory.
Prepare the files
Unzip the VivoW file to a folder on the root of your C: drive (makes finding the directory with the command prompt much easier). You can call it anything; lets say you call this folder “Android”. I found it easier to manage with all files in the same directory. I copied the files from Android\tools\win\ and pasted them to the root of the Android folder.
Prepare your phone
Turn off fastboot. Go to settings>power on your phone and make sure fast boot is unchecked. Turn on debugging. Go to settings>applications>development and make sure that USB debugging is checked.
Connect your phone via USB. Make sure it’s connected as charge only (a choice when you first connect it).
Open CMD.exe as Administrator
In Windows 7, the easiest way to do this is to put “cmd” in the search bar in the Start Menu. When it pops up at the top of the start menu, right click on it and choose “run as administrator”.
Navigate to your file location. For an Android folder located on your C: drive, it would look like the following:
Once there, you can test adb by typing “adb devices” at the prompt and hitting enter as shown above.
Run the VivoW script
If everything works and you can see your device ID, then you can move on to running the script provided. Type “hack-vivow.cmd” at the prompt, and hit “enter”.
At that point it does it’s magic. If it stalls, try it again. Sometimes it takes a couple of times. At the end, when it reboots you will be running good ole’ 2.3.3. and you are ready to root.
Run Revolutionary to get S-Off and Recovery
To run Revolutionary you just need to extract the zip file and click on revolutionary.exe to run it. Just make sure you have your Beta key ready in a text file to type in. It is case sensitive. This step will install CWM Recovery and is the last step you need to accomplish before actually rooting your device.
More detailed instructions on Revolutionary and obtaining root on your downgraded 2.3.3 Incredible 2 is available here: [How to] Root Your DInc2 Tutorial! (2.3.3 GB Only) - xda-developers
I hope this helps!
Edit: I have added the videos below to the original post as they do provide another way to "see" the process.