You're right, it still adds 30% DI at GM lumberjacking. The reason few people use it is because that 30% is subject to the overall 300% damage increase cap.
Why use 100 template points to accomplish something that can done by wearing the appropriate jewelry? Kind of sad really, the whole notion of items replacing skills.
What I find odd is that the Horrific Beast necro form also adds 30% DI while active, yet this 30% is allowed to exceed the cap (giving this necro as much as 330% DI).
Those wacky wacky devs I tells ya.