I was capped at 80+ pre patch with all settings maxed. After the patch I'm getting sub 10 FPS starting at the character select screen and it continues when in game.
There was no patch last night, it was just a few config changes around chat, zone channel, daily quest reset time and character transfers (http://tera.enmasse.com/news/patch-notes/patch-172903)
If you're seeing a huge drop in FPS talk to our CS folks and they might be able to help walk you through basic troubleshooting to see if something else is going on that is just now starting to show up.
Try alt-tabbing out of the game and back. Sometimes your video card doesn't detect that a game is running so it's clocks reduced to low power 2d mode. At least that's what happens to me (Sapphire HD 7850).