I have never been able to stack Muradin's with rain of fire, only hellfire. And because of phylactery, hellfire is no longer an option.

Yeah, sure that would be very nice if I would know exactly 85 seconds before pull, but I really don't consider that a realistic option though. Muradin's ramp up time and the fact that phylactery only procs by periodic ticks still lets me get a few stacks though. Of course, re-equipping is the optimal solution, but I can't imagine it working out for the better of the raid very often.

Muridan's spyglass stacks on damage not on spell cast. This is nice, in that if you SoC hits 6 mobs you get 6 stacks immediately. As HF and LT don't cause damage in the normal sense it won't trigger. So if you switched from IotDS to Muridan's thats why you can't use HF/LT. Both those still work with IotDS.

With Affliction you should base your trinkets depending on the fight. NMIC impressive numbers is based on stationary fighting with 100% time on boss and a "phase" change to sub 35% hp after 3 minutes. The further you move away from that type of fight the more attractive other trinkets look. For example, Blood princes. You have to change targets every 45 seconds NMIC is rather lackluster in this fight (Gunship also). But even on a fight like saurfang or putricide add priority is such that you may be away from the boss for more than the 8 second window a hasted corruption allows.

I think he's referring to health funnel.

Using my wowhead profile for my gearlist, 3.3.3 patch and 0_13_58. The profile is all 264 gear as I won't be going into heroic 25 ICC anytime soon.
Glyphs were Immolate, Incinerate and Conflag.

Global options were as follows:
Latency Low
Iterations 1000
Length 300 seconds
Vary Length 10%
Adds: 3
Fightstyle Patchwerk

I included almost every 219+ caster trinket (including some healing ones just for comparison since they are mostly straight spellpower) that didn't have hit on them since between our set pieces and the ashen verdict ring its easy to make up the rest of the hit.

Trinket	SimCraft DPS	DPS Gain
none	10073
Fetish of Volatile Power (245)	10318	245
Nevermelting Ice (232)	10358	285
Battlemasters Ruination (245)	10373	300
Sliver of Pure Ice (251)	10388	315
Eye of the Broodmother (219)	10406	333
Sliver of Pure Ice (264)	10412	339
Althor's Abacus (264)	10415	342
Illustration of the Dragon Soul (213)	10454	381
Althor's Abacus (277)	10460	387
Flare of the Heavens (239)	10490	417
spyglass (251)	10576	503
Reign of the unliving (245)	10611	538
spyglass (264)	10631	558
Phylactery of the Nameless Lich (264)	10654	581
Reign of the unliving (258)	10661	588
Dislodged Foreign Object (264)	10670	597
Phylactery of the Nameless Lich (277)	10730	657
Dislodged Foreign Object (277)	10765	692

This isn't perfect as it's not a BIS list and my parameters are not default but did this mostly for my personal knowledge and figured I'd share.