Ok let me get back to this once I test it with 3 kiels+ 2x expert rings.
Update:
3kiels + Fkatar + 1x Expert Ring= 100% reducts on aftercast delay. still cannot spam
3kiels+fkatar+2x expert ring= spam is slow, cannot even call it a spam really
3kiels+ fkatar + 2x expert rings+ link= almost no difference to the one without link but kinda helps. still rather pointless since you cannot cast another SB while the first one's animation is still on going. maximum you can get is 2 SBs, but that is on almost perfect condition.. it needs perfect timing, a good ISP and low ping. not good
so yeah, you really need 4 kiels, and obviously the after cast delays are not capped at 100%, seeing i had 100% on the first one but you still cannot spam and i had more than 100% on the others and the spam is considerably better.
So unless this would be changed somehow. Sonic Blow isn't really that viable. The only way you can use SB is by having 4 kiels and probably link, OR if you have Thanatos Card+ kitty claws+all the damage you can get(link,provoke) and hope for the best that one SB would be enough to kill people, sadly that isn't the case.
note: i would've been ok with the said delays, if katars were 1 handed like the bows. sadly, this suggestion would never be approved.