Whether rage loss is started at 3 or 4.4 is debatable.
My formula is based on official description
By default, berserk has lose 5 Rage per second
Each second, 20% more Rage loss Rate
If you are only looking at lose 5 Rage per second, it's 3 no doubt.
But If you take in the factor of Each second, 20% more Rage loss Rate, it is 4.4.
There is no official information on the reduce rage loss is based on 3 rage loss per second as you said, or it's counted as 40% reduced out of 20% more rage loss.
So I went for real experiment by comparing uptime shown that the time duration of rage loss is based on 4.4's formula set, if rage loss is starting at 3, the uptime will only last 19 Sec, chart is below.
The formula for 40% reduce rage loss if the fist second is 3
X=(5*0.6) for 1 second
X=(5*0.6)*(1+20%) for 2 second
or assuming both
berserk has lose 5 Rage per second
Each second, 20% more Rage loss Rate has reduced 40% loss, this could be another possible outcome.
The formula for above-mentioned is
X=(5*0.6) for 1 second
X=(5*0.6)*(1+20%*(100%-40%)) X=3*1.12 for 2 second
The chart and uptime is nearly identical to 4.4's formula set, and shown that it has suffer from low dps output for long duration of time before berserk ends.
By looking at the chart result and direct compare to video recording shown that my chart is very closed to official's calculation, feel free to flip back to the last page and watch my video, clear as that :)
If X is current rage state.
If Y is
berserk has lose 5 Rage per second
Each second, 20% more Rage loss Rate
The formula for default rage loss is
X=Y*(1+20%)
X=Y*(1+0.2)
X=Y*1.2
The formula for 40% reduced rage loss is
X=Y*(1+20%*(100%-40%))
X=Y*(1+0.2*(1-0.4))
X=Y*1.12
It is based on berserk has lose 5 Rage per second
Each second, 20% more Rage loss Rate has reduce 40% rage loss
with a compound interest.
I can explain Void period is actually higher than low rage berserk period, if rage avg is 0~15 during berserk, the total dps output is actually lower than cooldown Void period as it has 20 rage after 1.3 sec, 40 rage after 2.6 sec, and 50 rage at 3.9 sec, and there is no big DPS loss like you said if you are using 30% buff enchant if you count it all the factors.
Therefore rage has 40% reduce rage enchant and has got longer low rage duration, plus it has 6% less attack spd, 6% dmg reduction and 9% less movement spd compare to 30% buff enchant in the span of 10 out of 30 seconds for 1 cycle of berserk
We are looking at performance of both enchant under the same situation.
This proof that it doesn't have better QOL than 30% buff enchant, you must also count in the factor of cry wolf stacking :)