different thing is instakill, trying count it with dps can create meaningless numbers.
try and make test of this. take your instakill ability and tell me what dps you have. go on, try. and you will see that your numbers means nothing. trying apply that data leads to nowhere. why? because you try measure things with wrong measurement.
people fail to see difference between dps and damage. it is not semantic difference. as i said before, instakills can be expressed in kill count. but even this leads to very "ghostly" result, because why we need or we want dps meters in games? it gives very good idea what damage you can do with said weapon or spell. but in case of instakills... its too different. easiest way to see that yourself is said imaginary boss and you instakills. your dps is zero against it. and this is true. why? have to repeat a lot... its not dps(damage over time), its... well, its instakill. i have hard time to figure out why this is so hard to comprehend so easy difference:
a. damage over time(per second, minute)
b. instant kill.
dps is just a unit of measure. people invent various different units for good reason. their efforts of measuring something would make sensible information, if used right units on right target, that can create usable data to various applications later. weapon or spell dps you can measure and try to improve numbers you get.
lets imagine you got troll hp 1000 and your power word: kill, killed it. your dps is 1000? and if you kill kobold with 800hp then your dps is 800. and if your word have no effect on boss your dps is zero? now, tell me - what is your power word: kill average dps? 500dps? ok, lets pretend this is number we got from this experiment. how this number - 500dps, can help you improve your power word: kill? what excatly this 500dps for case of this instakill spell mean? almost nothing. there is not much sense. and here is why - instakills works very different, they are "success" or not "success" spells(in general). you need entirely different numbers from that troll fight to get idea what worked and what not, what to improve. and what numbers do you need to improve your instakill spell? you will want to see happened saves, saving fails, your spell level and all that dc stuff. NOT dps! dps as unit of damage measure for your calculations create unusable information.
and enough for me on this topic.