Kavan

The only difference between using strictly two cycles and interweaving is the ramp-up cost. The cost of ramping up comes up very frequently so it would be useful to get a good grasp of the actual cost. We don't want to look at dps lost. What we really want to do is treat the ramp-up as a dpm "cycle" and see what is the AB spam tradeoff compared to other fillers.

First a straight ramp-up as ABx4 assuming the debuff delay. For arcane/frost without CoE ramp-up is 3.46 dpm, Frostbolt is 3.4 dpm, optimum cycle is 3.04 dpm. Adding CoE Frostbolt improves to 2.99 dpm and optimum cycle to 2.73 dpm. Using a interweaved ramp-up of (AB-FrB)x3 we have 3.18 dpm for ramp up without CoE and 2.94 dpm with CoE. So it seams to me that the interweaved ramp up is even more efficient than just Frostbolt. This is with my gear so it's a bit biased but still.

Let's look at opportunity cost of using a suboptimal cycle for a specific amount of time. If we remember what the tradeoff means, it is the damage lost for each point of mana we're missing to sustain full AB spam. If we expand our formulas for multi-cycle situation we have:

T = tab + tc1 + tc2
M = tab * abmps + tc1 * c1mps + tc2 * c2mps
D = tab * abdps + tc1 * c1dps + tc2 * c2dps

Let's assume tc1 is a known quantity.

M = (T - tc1 - tc2) * abmps + tc1 * c1mps + tc2 * c2mps

Solving for tc2:

M = (T - tc1) * abmps + tc1 * c1mps + tc2 * (c2mps - abmps)
tc2 = (M - (T - tc1) * abmps - tc1 * c1mps) / (c2mps - abmps)

D = (T - tc1) * abdps + tc1 * c1dps + tc2 * (c2dps - abdps)

D = (T - tc1) * abdps + tc1 * c1dps + (M - T * abmps) * (c2dps - abdps) / (c2mps - abmps) + (tc1 * abmps - tc1 * c1mps) * (c2dps - abdps) / (c2mps - abmps)

D = T * abdps - tc1 * abdps + tc1 * c1dps + (M - T * abmps) * c2trade + tc1 * (abmps - c1mps) * c2trade

D = T * abdps + (M - T * abmps) * c2trade + tc1 * (c1dps - abdps) + tc1 * (abmps - c1mps) * c2trade

D = T * abdps + (M - T * abmps) * c2trade - tc1 * c1trade * (abmps - c1mps) + tc1 * (abmps - c1mps) * c2trade

D = T * abdps + (M - T * abmps) * c2trade + tc1 * (abmps - c1mps) * (c2trade - c1trade)

With this in hand we see that if we set tc1 to 0 we get the already known equation. Now we want to see what is the opportunity cost of having a tc1 > 0 which would correspond to the time spent on ramp-ups. First tc1 * (abmps - c1mps) is how much more mana we would have to spend to get to full AB spam. Typical values would be -24.35 mps for ramp, 262.39 mps for AB spam, duration of one ramp-up 12.93 sec. Together ~3700 mana for one ramp-up.

So in the non-CoE case a ramp up when using the optimum cycle costs us 3700 * 0.14 = 518 damage or for CoE 3700 * 0.21 = 777 damage.

So the real cost of having to do one ramp-up is less than 1k damage.