wasting Lava Burst Crit?

nvm.

For the record, EM makes your next CL, LvB or LB instant, it's (no longer) not related to crit, but gives a 15% spell haste buff for 15 seconds. It basically makes FS & LvB go off at the same time. The only waste i see here is that it's not using the longest cast (LB). The burst this way is pretty nuts, which is prefer for the way i play.

Depends on your click.

The default order should be:
a) Flame Shock (which is instant, and therefore cannot consume Elemental Mastery).
b) Lava Burst (which will crit and be instant via Elemental Mastery).
c) Chain Lightning (if you include this in your general DPS sequence... some do, some don't).
d) Lightning Bolt (as the fall-through).