Astral Fire/Umbral Ice timers are actually bad mechanics at a meta level.

[Grimoire-M]

I have to somewhat agree with Rongway's conclusion that Fire IV would need something else gating it to make this work. My issue is more with the framing of AF/UI as being bad for having the tension they do. It would be difficult to maintain the same level of forethought that the timers do encourage you to have once you start accounting for how some of your mobility options come into direct conflict with them. Particularly when you factor in that it also rewards you for gearing into spell speed and using Leylines in particular. My overall interpretation of the job is that the reason it's a successful turret mage is because the timers allow for some level of flexibility while still putting some rails on how you handle things, and Polyglot and Fire IV both were ways to reward you for maintaining those timers (Fire IV more for Enochian, specifically in regards to HW). And then you get into edge cases. Manafont doesn't work unless you have a timer. Firestarter and Fire I/Paradox have no explicit purpose without that timer. Some of the value of Triple/Swiftcast is lost without those timers. It adds tension, sure, but not excessively so, because it doesn't ask that you juggle a bunch of secondary resources. Astral Fire and Umbral Ice are the core, including the timers themselves. At some point you have to ask, "Does taking this away add anything?" And judging by the hoops Rongway jumped through to get it to work without it, I'd say no, which is distinctly different from how Monk was handled previously. And honestly new Summoner gets punished more than Black Mage ever has by downtime, which isn't something I ever thought I'd say given where both were back in 2.0.