[TBC] FPS tanking below 60 in random periods during gameplay

Hey guys so ever since I started playing on the new Outland TBC realm there have been random occasions during gameplay where my fps suddenly tanks below 60.

My system specs (i7 6700k/GTX 980 ti) are more than capable outside of major towns & cities (where there isn't 500+ players in a small area) of achieving 60+fps 100% of the time. So I was wondering if anyone else has experienced this and has anyone else manged to find a fix for this?

I know it isn't addon related since during questing I only have 4 enabled (Quest Helper, Cartographer, Bagnon & Gatherer) which are not known to cause performance issues (the fps drops even when addons are disabled). Heck i've even gone as far as reinstalling the client which hasn't solved the issue either.

For example here is a location in STV where this issue has occurred:

http://imgur.com/a/0f7nB