For those who encounter the same issue (whether using Lotro or not), this is how I was able to get it running.
First, you will need to install primus.
This is in the Bumblebee PPA, so if you are using that then skip the following command.
To add the PPA, open the terminal and enter the following command:
sudo add-apt-repository ppa:bumblebee/stable
sudo apt-get update
Once you have added the PPA, install Primus using the following command:
sudo apt-get install primus
If you have a 64bit system (likely), they you also want to use this command:
sudo apt-get install primus-libs-ia32:i386
Just like with optirun (Bumblebee), Primus uses primusrun.
To be technical, here is a quote to explain the difference between the two:
Bumblebee uses VirtualGL to copy the image generated by the second (faster) GPU to your display. VirtualGL was intended for use over a network though, so it takes a great many steps to enable this (compression, sending the image over a network link, decompression, etc).
Primus doesn't perform all these "extra" steps, instead taking a more direct route (copying the rendered image in memory to the other GPU, then displaying there). In theory this should get you better performance as well as better compatibility. Running applications will "see" the OpenGL implementation of your real hardware, nothing virtual is presented to them.
The next step I took was to use the Windows version of PyLotro, since the Riders of Rohan update caused issues with the Linux native PyLotro app.
I set up windowed mode, and started PyLotro with the command 'primusrun wine pylotro.exe'.
This started Pylotro as it had done in the past, but once I clicked to log in, instead of getting the annoying 'FINISHED' message, it started the game and the problem was gone.
So, if you have problems running Wine apps through optirun, I recommend trying primusrun, as it seems to work a little better.
(The solution found was thanks to webupd8, see the page here: WebUpd8 Primus Page)