In general, you want to wait until 5-6 stacks, refresh SWP/VT, then hit DP and cast as much MF:I as possible.
Why?
I'm going to make comparisons by simply going through the 10 seconds, choosing different spells to cast, and multiplying their spell power coefficients by the spell power given by however many stacks of the BBoY proc are present at the time. I'm also including the damage constant. The better choices will have higher total (damage constant + SP coefficients * current spell power from the proc) during these 10 seconds.
For instance, if we get our 3rd orb right as BBoY procs and has 1 stack, we can cast DP right away, channel as much MF:I as we can, and then refresh SWP and VT. In this case, we may not have even noticed the trinket proc yet and have already cast DP, but we'll still use this case in the comparison. We need to find out more specifically the numbers we're dealing with, such as exactly how many ticks of MF:I we're be seeing. In this case, we may already know that we can get as many as 11 ticks of insanity, but for most other cases, we'll also be channeling MF for a few ticks here and there, and so I came up with a time line graph to keep track of what's being cast when and how many stacks the trinket is at. It turned out to be a pretty big monster, and I even left out some of the possibilities once other combinations made certain patterns clear.
(Click to Enlarge)
This gives a pretty good idea of what we're cooking with. The idea was basically just to make sure the right number of MF and MF:I ticks are used in the different areas between refreshing dots or using mind blast and to see how many stacks of BBoY we're getting for each spell we cast. You'll notice that most of the iterations have MB at the far left. To keep things even, I assumed for most of the options that you just cast Mind Blast right as the proc happened. If you cast your 3rd Mind Blast earlier, then you probably already dumped your orbs into Devouring Plague and the whole discussion is moot. Therefore MB is included in each case at least once. Where exactly it is in many of the cases isn't a big deal and the overall findings hold true if it were to be moved around and compared to other possibilities with similar changes to MB.
After I tallied up all of the ticks and kept track of how many stacks the trinket was at for each cast, I simply plugged those into a spreadsheet that multiplies the SP coefficient of the spell by the spell power granted by the trinket at the time of the cast (and included the static damage portion of the spell as well). My numbers are all done using a 561 BBoY, but you can do the same with any of them. Make sure that you multiply the int proc by 1.05 (for 5% stats buff) and by 1.10 (for the 10% spell power buff) to get the total spell power you're getting.
Anyway, here's what I came up with for each of the possibilities on the time line:
* "DP at X w/ 2nd MB" above does not include 4pc t16. Using another MB after DP during the BBoY is a great choice if you have the 4pc t16. *
The explanations of these in the chart may be next to useless, but each case here correlates directly to one in the timeline graph above, so look at that if you want to know exactly what's going on in each case. A few trends stuck out that helped to eliminate some combinations. Yeah, this wasn't all of them. First, using DP early on is basically always bad. DP and MF:I are just too powerful to miss out on the massive spell power gains from the trinket. This is even more true for DP than for insanity. Another theme present is that being able to snapshot a high stack of the trinket with one last MF:I cast is great. You want to at least delay DP long enough that you'll be able to do this. Refreshing your VT and SWP is a good way to spend some the time as you're waiting to get to 7-9 stacks for your DP. It tends to be better to refresh them first, waiting for medium-sized stacks, and use the very highest stacks for DP/MF:I. This surprised me, as I expected stopping MF:I to cast them at 9-10 stacks would be pretty awesome. It still is, but there are even better ways to handle the trinket. Lastly, recasting your Mind Blast after DP isn't that bad. In the bigger picture, it's going to be even better than this chart shows because it's not looking at the delay of your orb generation. Also, Tanned pointed out to me that the 4pc T16 will be affecting this MB. If you have 4pc T16, it's best to use your next MB during the BBoY proc. Thanks, Tanned!
Well, there you go. I hope that this can put some minds at ease. Please send me a message or leave a comment to let me know what you think, and always send me more questions and ideas!
