Raging strikes was 20% on a 180second CD, (Only Bards got the 120 second variant through a trait). This is a 11% uptime on a 20% damage buff, so effectively about a 2.2% damage boost. This is made up with Improved Enochian, which puts the black mage from 105% to 110%, an increase of approximately 4.5%.

Likewise, we are comparing 286 potency (260 x 1.1) to 294 (280 x 1.05)

With the current cast time of 2.8s (compared to 3.0 in HW), this means the potency loss is ~3 potency per second in the grand scheme of things.

Foul is 680 potency every 30 seconds + cast time, so we'll use 32.5 seconds per Foul, which is a potency boost of 20.9 potency per second.

In terms of 'losing damage' in the transition, black mage lost none, and the changes in 4.05 only cemented that further. We gained in damage and mobility. That isn't to say we aren't in a less than stellar spot at the moment, but don't spread misinformation.

Stormblood is an improvement in terms of damage.