In a heavy DPS situation, EM is best to use with Lightning Bolt, not LvB or CL, as it is the longest cast spell out of the three and gains the most benefit. I've always been confused as to why people use it with LvB.

As well, you should cast LvB -> LB -> CL instead of LvB -> CL -> LB, as that ensures that Clearcasting is up for CL. The projectile travel time on LvB means if you go LvB -> CL, the buff may not yet be up for CL.

Of course, some of this is hard to setup properly in castsequence/click macros. :P