Yeah the Shadowburn + Havoc combo is lethal and awesome.
It really pays to make mouseover macros for them. And learn to use them.
Shadowburn macro:
Code:
#showtooltip
/cleartarget [@mouseover,harm,nodead]
/cast [@mouseover,harm,nodead][]Shadowburn
/targetlasttarget [@mouseover,harm,nodead]
Havoc:
Code:
#showtooltip
/cast [@mouseover,harm,nodead][]Havoc
To make the most efficient use out of them you'll also want to enable nameplates and probably use an addon like Tidyplates to make mobs with <=20% health more obvious and easier to target.