While testing some mage weapons with Gaabob, we decided to see what the bear debuffs actually do (spoiler: they both reduce armor).
As in the description, maxed Hellscream reduced damage by 50, and Hit% by 25%.
Most people are aware it also stuns though it's not in the description. In testing it also reduced armor by 10.
As in the description, maxed CB reduced damage by 50 and Dodge by 25%. In testing the skill also reduced armor by 29. This figure is unusual. It would be interesting to see if it is just the way 30 rounded in our case, or what. It would also be interesting to know how this effect of the skill scales with rank, and if affected at all by stat driving (I doubt it).