I am currently using

#showtooltip Lava Burst
/use 13
/use 14
/cast Elemental Mastery
/castsequence [target=focustarget,harm][] reset=target/combat Flame Shock,Lightning Bolt,Lightning Bolt,Lava Burst,Flame Shock,Chain Lightning,Lightning Bolt

But this is for PVE ONLY. I use a mod called "ActionBarSaver" and it lets me keep multiple action bar configs, I have one for PVE and one for PVP. For PVP, I have seperate buttons for flame shock, LB, CL, and Lava Burst and micromanage the casting of all of them, since I will want to sometimes consume Flame Shock right away sometimes and use chain lightning more often. I might take CL out of the macro above completely and replace with a LB, since the mana cost of CL is so high and for many boss fights you only need it at specific points.