For general reference, this is how I calculated the fastAttack delays for Prime Blow and Another Blow:
32121011 is Prime Blow. It has an addAttack effect which chains it to Another Blow (32120052), with a skipActionFrame of 9. Going off its default delay 1260ms, this cuts out 3 frames [9, 10, 11], reducing it to 810ms. Another thing to note is the "isAuto" tag, meaning that Another Blow appears to always occur after you've learned it. Another example of this tag existing is Mercedes' Charge Rush, where the rushing action will automatically chain to the tossing action.
Taking a look at the new fastAttack effect, there is a randomSkill value, which can pick an alternative skill effect other than the default Prime Blow. i.e. you will see First, Second, and Third Blow skill graphics as a possibility as well as Prime Blow's effect.
The startRepeatActionFrame seems to dictate the starting frame in the delay, and the endRepeatActionFrame dictates the ending frame in the delay for when a "fastAttack" is used, i.e. repeatedly spammed. The delays for all Blow skills (except Another) are identical, with possibly the exception of character position, but I didn't look at that. This start and end cut the delay down to 480ms. When we combine that with the skipActionFrame in the case of chaining to Another Blow, we cut the 9th frame (which still exists as the endRepeatActionFrame) out, which is another 90ms, leading to 390ms Prime Blow.
The startRepeatEffectFrame dictates the starting frame for the effect of the skill. If we were to look at First Blow, the first four frames [0, 1, 2, 3] are used for the twirling effect of the staff, which exists for Second, Third, and Prime as well. Frame 4, which this effect tells us to skip to, is the first frame that the slashing motion occurs. Thus, in effect, each time you continue a fastAttack, this is analogous to skipping the "start up" involved, where the Battle Mage twirls his staff, and you go straight into the actual attacking part of the animation, which is why you only see the attacking portion in the videos posted so far. This means every time a Battle Mage stops chaining Blows, his next initial Blow will have an additional 420ms (or 330ms if you have Another Blow, leading to 810ms for the first attack, or 720ms with Another Blow). If a Battle Mage doesn't chain his Blows, they will be 1260ms in duration instead.
The same effects are applied to Another Blow, but it has slightly different delay values. The principle is the same, and its delay gets cut from 900ms to 450ms, cutting out 3 frames [7, 8, 9], with no skipActionFrames. Since Another Blow's animation doesn't have any superfluous start-up, the entire effect is present with the startRepeatEffectFrame = 0, starting from the beginning and playing the entire thing.
I personally find this to be a fantastic way to make the class less stale. Rather than being forced to use weaker skills to chain to stronger skills like Aran, you have the graphical appearance of your earlier skills mixed in so it's less spammy looking, and the attack patterns flow very well. That being said, basically all the Hand skills are pretty pomegranatety, with terrible DPS in comparison, and only useful for utility that's meaningless for training since things should be dying in one or two hits, and bosses because they can't be knocked back, slowed, or stunned in most cases.
For reference, Normal (6):
|First Blow||Triple Blow|
|Second Blow||Quadruple Blow|
|Third Blow||Quintuple Blow|
|Prime Blow||Finishing Blow|
|Another Blow||Battle King Bar|