Agreed, but casts don't kill mobs, ticks kill mobs.
Your math is solid, but I feel that focusing on the cast is potentially misleading. So I thought to myself "how would I model this on ticks, instead of casts".
So I built this spreadsheet:
https://spreadsheets.google.com/ccc?...thkey=CKzT1K0O
and plugged in some numbers that seemed reasonable, and used some random simulation to model 10 encounters with a mob or set of mobs.
What it told me is that, other than crit-fishing, it is very rare that a mob would die faster in the U7 system than in the U8.
For bosses, etc, the ability to crit-fish is nice, and for those situations, I think the U7 system would be superior. But for trash, etc, I think I like U8 better. Which is not what I was expecting.
Note that I cheated a bit - setting up the per-tick damage for all 10 scenarios for the U8 system would have been very tedious, so I just averaged the damage.