I dunno, you expectation of casters may be a bit high..
Did lots of epics lately and never really saw them insta killing the way lacer/teth/ayspam can do. Those last few points of DCs those guys have kinda put them in a league of their own far as that goes.
Most casters can kill some stuff sure, but for the most part they still see a ton of saves, so theres plenty left for me to kill.
EVen playing with other completionist casters, none really even came close to my killcount. Especially in VoN5epic, had a completionist sorc speced for necormancy, he did what he could, but the saves there are pretty high so think thin he came in a distant 2nd in killcounts behind me.
Just a huge gap in the abilities of maxxed out multi TR'd veterans, and "decent" endgame casters atm.