Hrm. You should be getting a lot less of that with the arguments than without. Try upgrading your java to u51.Are the settings in the OP optimal for single player offline use? (related: is that SSP?) I thought maybe I'm applying these settings incorrectly and it might be adding to my troubles with my game.
I am overwhelmed with "Memory overburdened" errors in the console with Permgen set to 256 instead of 512 in either FTB or MultiMC5 launcher.
I am also seeing lots of " Can't keep up! Did the system time change, or is the server overloaded?" messages and a weird skipping lagginess. Punching a tree will get the wood, then pop back into place and need punched again, animals will freeze then jump 10 blocks when I try to punch them. It can be as frequent as every two minutes.
Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz
NVIDIA GeForce GTX 560M
Win 7 64-bit
MultiMC5 (preferred, FTB launcher sames issues)