So I was trying some new builds to amuse myself, ones that would mix up Sab + NB, with some Sin for extra DPS. One I tried was sorta pvp'ish, going 32 in NB for Fell Blades (yes, I should've realized Sab abilities don't proc weapon enchants so this fails, but read on anyway):

Idea was to use Shrapnel to spread around Fell Blades. Also, mix in some SOD for fun with the following rotation:

Shrap 5x -> SOD -> Shrap 1x -> Detonate

I found out SOD won't proc off the charges or the Detonate. Is this a bug? I guess it's like weapon enchants not working, either.

I did discover that a 5 charge Detonate nicely cycled Heat Retention. With that thought in mind, I decided to try a more Sabby build that rotated Spike Charges with Ember charges (since Ember is non-physical and would get buffed by Heat Retention):

I discovered that 5x Spike will only give 1 (one) stack of HR, not the 5 that other charges. So this rotation mostly fails - 5x spike only give 1 HR, then 5x Ember + Det gives 5 HR but doesn't benefit from the 5 HR because the next cycle of Spike eats the 5 HR stack and leaves 1.

I think 5x Spike -> Detonate should yield a full 5 stack of HR, and the behaviour is flawed because the system lumps all 5 Spikes together into a single DOT.