Hey there! I'm one of the main bumblebee devs (nice to meet you) and happen to use minecraft/technic myself...
To correctly use technic with bumblebee, the easiest way is this:
optirun bash
java -jar path/to/techniclauncher.jar
Keep the window open while playing, then when done type "exit" to shut down your nvidia card. It's a little crappy for now, but it works... Things should get better when optimus support is in the mainline kernel (a few more months, if we're lucky!)