Could you please check and confirm the version of Lightroom?
Running OS X 10.11 El Capitan on a 27 inch iMac late 2013. After the 6.2 update, my LR became unusable (always crashing when using external plugins as Color Efex Pro/Silver Efex Pro). My solution was simple: restore version 6.1.1 via TimeMachine backup before the 6.2 upgrade. Now it's all ok.