Actually, FF6 speed sucks really bad at determining first turn initiative due to the starting gauges being randomized. It's theoretically better at doubles than at determining initiative, which is heavily randomized (although this is mitigated by menus. ATB fails).
Actually, FF6 initial ATB gauges are NOT entirely randomized. They are...to an extent. The game puts weight into those with higher speed though. By this I mean the game will usually make initial ATB gauges reflective off your speed stat.
Say we have Locke, Relm, Terra, and Cyan using their default set ups. This is a pretty wide curve, hence why I chose those 4 specifically.
In most cases, the initial ATB gauges will look something like Locke > Relm > Terra > Cyan. Now, how much can vary, and there are cases where, say, Terra will have more than Relm, or Relm than Locke. In VERY rare circumstances, Cyan will have more than Locke, but that's happening about as often as Yangus going before everyone else in DQ8.
Furthermore, Relm might start with a higher ATB gauge, but its possible that Locke will still go first anyway, thus offsetting the initial ATB advantage.
So the end result? The gauges are randomized, but it still allows faster characters to go first far more consistently, and this isn't a case of law of averages; its a case of its randomization being geared in favor of faster characters.
Granted, Kefka's fight, everyone starts with a full ATB gauge, so you could just say this offsets everything. Personally, I'm inclined to either throw that quirk out entirely, given its clearly an aspect related to the whole Tier nonsense and nothing else.
Next off...Kefka and Zeromus are pretty opposites actually in regards to speed. Play an SCC, Kefka's speed really shows. Meanwhile, Zeromus wasn't actually doubling as much as you'd think when I had to solo him with Cecil (...granted, I never actually won that fight due to him putting me on such a defensive in the second half to the point where I'd just run out of Elixirs.)
Zeromus getting constant turns is a quirk of FF4's Primitive ATB. If you waste any time selecting commands, enemies gain more turns (time spent in actual menus ala Item or Magic need not apply; Wait kicks in there and thus time stops, etc.)
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On a completely different FF6 note unrelated to Kefka...
For people who allow Gogo to use skills, should be worth noting that he should pretty much decimate the rest of the field (if nothing else, Sour Mouth = Win for most fights right there.)
