I've had this issue with Mint 18 Cinnamon...
I'm a computer science major, I bought a new notebook for class... I enjoy Linux Mint and Ubuntu... I enjoy the regular updates, software updates, amazing peer support options (IRC, forums, etc.), and how it just works... Do an install and most drivers and applications I need are there... I just enjoy the way the OS works and the way so many drivers and applications are packaged in the distributions... Although I must admit that I bought Office 2010 and run it using WINE as I was having issues with a few things I needed for class with Libreoffice, but still it was very reasonable... plus I own it, can continue using it... For me, linux supports applications that will do most of the tasks I do for casual computer use and school computer use.
I ended up using Alchemy on the notebook, but I had the issue with the SL viewer too... For me, Alchemy and Firestorm don't have those issues.
I find Alchemy to have less laggy chat performance, so I will alternate between the two based on what I'm doing... if I'm having an in depth conversation I use Alchemy, if I'm at a live music event I enjoy Firestorm.
I suggest trying another viewer. Unless you *Have* to use the SL viewer, firestorm isn't all that difficult to adjust to.