Vengeful cry + berserk?

The new warcary vengeful cry prevent inherent loss of rage.
Will this also apply to berserk?

unless they changed the meaning in 3.25, no. Just like how inherent loss of rage is X% slower doesnt effect Berserk/RVoB, this will not stall the loss of rage by those skills. It only effects the rage loss when you aren't gaining rage.