I have an idea about how to think about the 2 target rupture cleave scenario but I haven't had time to experiment with it.
A couple weeks ago I did a little test in ShadowCraft to motivate the analysis but never got around to doing the analysis. I hacked ShadowCraft to handle two different situations, first a situation where your rupture is being applied to 2 targets with no loss in envenom uptime, basically I magiced combo points out of midair to see what would happen, then I did the same thing but this time counting those rupture cps against the cp resource pool leading to less envenom and less envenom uptime.
Results:
Baseline DPS:333676.7
Code:
yellow_hit: 3.05916649119
agi: 2.95938919146
dodge_exp: 2.19118094382
haste: 1.50391975236
crit: 1.45050882244
mastery: 1.38738064897
white_hit: 0.794424029684
2x Rupture Magic CPs, DPS: 455191:
Code:
agi: 2.88066816289
yellow_hit: 2.56300034594
dodge_exp: 1.6900302358
mastery: 1.47025930377
crit: 1.30078718002
haste: 1.03214424645
white_hit: 0.58568763657
2x Rupture Real CPs, DPS: 422238
Code:
agi: 2.94202222731
yellow_hit: 2.75815658063
dodge_exp: 1.86637584522
mastery: 1.47123320699
crit: 1.41779728445
haste: 1.17665594637
white_hit: 0.620148701929
This basically follows expectations, in our magic CP case the value of haste declines substantially because of the substantially increased energy regen and it is somewhat stronger in the real CP case but energy regen is still higher than before. Mastery substantially increases in value from the additional VW and dp ticks and crit loses some value from the additional energy regen although it does lose less value because of the crit is less dependent on energy regen.
TAKEAWAY: The reason I didn't want to share this simple test is simply that its incomplete, it assumes that the player somehow keeps a 5 pt rupture and full dp uptime on 2 targets. This is somewhat unrealistic and likely biases the results somewhat, I suspect toward mastery because lower cp ruptures have lower energy efficiency but I'm not certain. There is a lot more to be done here but the basic results do appear to confirm that mastery increases in value haste decreases in value and crit remains relatively stable in a two target rupture multidotting scenario however this analysis probably isn't precise enough to quantify the magnitude of the effects.