Ok, this is just me thinking of a work around, so I have not had a chance to actually test this. By putting a number of commas in castsequence, you can effective run two castsequences in one macro. exampe:

Code:
/castsequence Flameshock,,,,,,,,,, Lightning Bolt,,,,,,,,,, Lightning bolt,,,,,,,,,,,, Lightning Bolt,,,,,,,,,,,,,,,,, Lightning Bolt,,,,,,,,,,,,,,, Lightning Bolt
/castsequence ,,,,,,Lavaburst,,,,,,,,,,,,Lightning Bolt,,,,,,,,,,,Lightning Bolt,,,,,,,,,,,,,,Lavaburst,,,,,,,,,,,,Lightning Bolt,,,,,,,,,,,,,Lightning Bolt
Now the commas will naturally have to be adjusted based on your keypresses per second and where in the rotation the spell is supposed to go off, but they basic idea goes that only 1 sequence should be "up" at any given time, and shouldn't be subject to the "get an answer back" lag found in castsequence.