My problem with Thermodynamicity and Pyromaniac is that both are heavily random.
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On tranquility psion I rarely find it optimal to alternate between fire and ice. 95% of the time I would prefer to either just spam ice, or use something from psychokinesis and/or thought control. Getting a good AP cost reduction on something I don't actually want to do most of the time (alternate between fire and ice, that is) is redundant.
Mmm. You don't sequence your abilities well, then. Chill is a fairly weak debuff; burning is one of the strongest debuffs against living enemies - it's the only DoT + fear, I think. So what you'd want to do is open with, say, a premeditated cold ability like Cryo Orb, then use Pyrokinesis, pick off a survivor with Cryokinesis, and if you're dealing with a huge mass of enemies, then place a ThermoD, proxy a TK Punch for the ThermoD kill, Cryokinesis to kill anything that's not yet dead or on fire, and pop a psi booster then throw a grenade. All that in one turn is no problem with Thermodynamicity.
It's even often nice when you're not using Metathermics as your primary output, since it lasts a turn. You can cryo shield yourself one turn, immolate the next, and do all that in the little sliver of AP you leave yourself between double Electrokinesis each turn, or Implosions, or whatever. Industrial Robots are no threat at all - literally zero threat - if you can walk two squares and be immune to fire, so a few fights that could otherwise get hairy become predictable and safe. Crawlers of any sort are loath to get up close when you're surrounded by fire, so you can make some ruckus, start burning, and then have a low-AP Cryo Orb to reveal crawlers in a huge area once you've given them a turn to get close - then with the rest of your AP, and a quick-cast Pyrokinesis, you can manage a room with no risk to yourself.
There's nothing random about Thermodynamicity. It's best against large groups, or extremely tough enemies, and isn't something that you use in every single fight, unlike Premeditation, but it's top-tier if you play to it.