This is a longshot, but what about another click to force the proper sequence? Like :

Code:
2 - Use Berserking and cast Chain Lightning
#showtooltip Chain Lightning
/console Sound_EnableSFX 0
/cast berserking
/castsequence reset=4 Chain Lightning, Elemental Mastery, null
/console Sound_EnableSFX 1

3 -  Cast (instant) Lava Burst
#showtooltip Lava Burst
/console Sound_EnableSFX 0
/castsequence reset=8 Lava Burst,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
/console Sound_EnableSFX 1

New #4 - Chain Lightning
#showtooltip Chain Lightning
/console Sound_EnableSFX 0
/castsequence reset=4 ,,,,,,,Chain Lightning,,,,,,,,,,
/console Sound_EnableSFX 1

5 - Fill in with Lightning Bolts and throw Bloodlust
#showtooltip Lightning Bolt
/console Sound_EnableSFX 0
/castsequence reset=300 Bloodlust, null
/cast Lightning Bolt
/console Sound_EnableSFX 1
Leading the second Chain Lightning with commas should let you drop LBs until CL is up again. Like I said, longshot, but maybe? *shrug*