Panzermeyer, all the responses to your questions are detailed in the build in the first post of this thread.
Basically you have to decide if you want to go fire elemental and shiradi, or go water elemental and draconic.
I choosed water elemental and draconic because the bosses in epic elite have tons of hit points and I need to deal as much damage as possible with creeping cold and greater creeping cold.
Nothing prevents you from transforming in fire elemental while using draconic destiny and cast wall of fire and body of the sun,
or nothing prevents you from transforming in water elemental and cast creeping cold dots while using shiradi destiny.
Against trash mobs I do about the same damage when in shiradi (fire) or draconic (ice), but draconic shines against bosses when I use creeping cold spells (I'm usually busy to run while fighting a boss, so I don't have the time to cast spells other than creeping cold dots. creeping cold is not famous for proccing shiradi a lot ).