So I've been hearing some people lately with some FPS issues when we have an encounter with something that is graphic intensive. I used to have this problem before I built my computer here a few months ago. When I played on my laptop, I used this macro and it helped me out a lot.

/console showdetaildoodads
/console showlowdetail
/console horizonfarclip 1305
/console farclip 177
/console groundeffectDensity 16
/console groundeffectdist 1
/console smallcull 0
/console skyshow 0
/console detaildoodadalpha 0
/console characterambient

I just made it a macro, and whenever I logged in, activated it. For me, it reset the settings after I logged out and logged back in. If that isn't the case for you, and you want to go back to your normal settings after using this macro, then go to your WTF folder and delete your config file. Hope this helps.