The new Worm and Hircine post-Stonethorn give 145 Magicka or Stamina Recovery, respectively.
Pre-Stonethorn Worm and Hircine giave 4 percent cost reduction to Magicka or Stamina abilities, respectively.
So how do we convert Recovery to cost reduction?
To put it simply, we change the Recovery to a per second value and compare it via proportions to cost reduction. The math is in the video, but I have it below as well.
New value is 145 Magicka/Stamina Recovery.
Recovery is 1 tick every 2 seconds, so divide by 2 to get a per second value.
Old Worm/Hircine was 4% cost reduction.
So we have the proportion 72.5/x = 4/100.
Solving for x gives us ~1812 regen per second.
We can adjust the Recovery value according to which buffs we have active.
Assuming we have our typical Recovery buffs, the changes to Worm and Hircine are going to be a buff across the board for DPS.
It is very rare for any PvE spec to be running very high regen, so it is almost universally going to buff sustain for all roles.