help me better my shadow priestyness :D

[Hoddie]

I'm not more likely to miss a spellcast during a mastery proc than outside of the proc (also, missing MB does not affect it granting Empowered Shadows). I'm not more likely to miss a spellcast during a mastery proc than I am to do so during a haste proc or an int proc. The possibility of missing during a proc may affect the variance of my DPS from fight-to-fight, but not the average.

You're not more likely to miss a spell with a mastery proc than an int/haste proc, that's not what I said, but if you miss a spell that would otherwise extend your proc, that's a big deal. You can extend the mastery proc by casting MB just as it ends, and extend it further by re-casting VT and DP as the Empowered Shadow buff is ending. Effectively you can extend a mastery proc twice, for example with Theralion's Mirror you can get (on average) 55 seconds of mastery-proc buffed DP every 112 seconds, but you lose 24 seconds of that if the DP that you cast at the end of the ES buff misses.

[CaseyTheRetard]

We do the same thing with any other kind of proc trinket, cast a DP at the end of the proc. For a mastery proc, you can lose at most 24/(39 + <proc duration>) of the value of the proc's effect on DP. For a non-mastery proc, you would lose 24/(24 + <proc duration>). You stand to lose more of the proc's effect on DP with non-mastery procs than mastery.

In any case, "cast DP at the end of the proc" typically occurs 2-3 GCDs before the end of the proc when you know that casting another Mind Flay will lose you the opportunity to extend DP - plenty of time to recast once if the first DP misses. Given that current theorycraft shows that hit and mastery are better stats than haste between the breakpoints for VT ticks, the argument is probably moot for anyone in 378 gear. They should be hitcapping regardless.

[Hoddie]

We do the same thing with any other kind of proc trinket, cast a DP at the end of the proc. For a mastery proc, you can lose at most 24/(39 + <proc duration>) of the value of the proc's effect on DP. For a non-mastery proc, you would lose 24/(24 + <proc duration>). You stand to lose more of the proc's effect on DP with non-mastery procs than mastery.

Kind of going off on a tangent here which is probably my fault, but a mastery trinket's value is rated assuming you squeeze out the 39 + <proc duration> every time. The only way to squeeze out that value is through DOTs, and missing either of the final 2 DOT casts means that the trinket's value is not fully realised. In that 39 seconds + <proc duration> you might cast only 6 spells that benefit from the proc - if you miss the final one you've lost 1/6th of the benefit. An intellect or haste proc on the other hand affects every spell that you cast. You might cast 15-20 spells during the <proc duration> so missing one spell isn't as big a loss, even if it's the one that would lock the proc into a DP for an extra 24 seconds. You could drill down into the coefficients and everything else to work out what % loss a missed final DP would cost you in each example, but hopefully this explains why I believe it's more important to be hit capped with a mastery trinket than it is with an int/haste trinket.

[Zuziza]

You can extend the mastery proc by casting MB just as it ends, and extend it further by re-casting VT and DP as the Empowered Shadow buff is ending.

Missing MB would not affect your ability to extend the benefit of a mastery proc towards ES. You get the buff from casting the spell, not from it hitting a target.

[Hoddie]

Missing MB would not affect your ability to extend the benefit of a mastery proc towards ES. You get the buff from casting the spell, not from it hitting a target.

I didn't say it would.