Felstriker probably isnt worth it IMHO, because in kronos armor values are blizzlike, Offhand weapon is more than just a ragefeeding statstick, it actually does considerable damage.
However Ironfoe...
2.4 speed with %80+ flurry uptime, battle chicken, juju flurry and head/leg enchants, also 10BTs/5WW and a few OP per minute would get you about 48-52 Main hand attacks that can trigger the proc.
In short, with %10-11 proc chance you will be getting 5 procs per minute if you are buffed to the teeth.
Thats 10 extra white hits, with Main hand which benefits from AP %100.
Assuming you are human with %12 hit, %85 glancing blow damage, 2.1k AP, %40 crit (those values are easily attainable with world buffs).
from hit table
%15 miss>%6~ dodge>%40 glances(that do %85 damage so its %34)>%39 crit(%78)
%112
So, with those hit/crit values you are doing 1.12 of your normal MH damage by average on every hit.
with 2100 AP, %5 DMF(or sillithyst, this can be much higher ofc) , (73-136 + 2.4*2100/14)*1.05 = 455 - 521
(488 average damage)
488*1.12*10=5464 damage per minute =~ 91 DPS (Keep in mind this value will be reduced by armor)
This is what my calculations show me, it grants you about 91 Dps(Before mitigation) at the cost of losing some 15-20 Main hand dps as well as negligible WW/OP damage loss. You also get a chance to generate rage with your Main hander while using HS/Cleave. It's probably amazing...
NOW IF ONLY IT DROPPED
(please correct any assumption/calculation i have done wrong in this post)