The druid just spends to do what an animal would, yes.
Keep the fiction in mind though: a bear has "tear someone apart" which means some poor human is probably dead, but something like a treant? Probably not. It'll hurt and might, say, rip of some branches that won't be there anymore to smack you, but not outright kill.
They way to look at the druid's shapeshift is that it's a bit more like saving up a success for later. Turning into a bear does give you some "free" attacks, but only as a bear would, nothing fancy like the fighter might attempt to disarm or something. Basically the druid is locking in some future successes at the cost of the animal's limitations.
By "limitations" I'm just thinking stuff like "oh crap there's a bear I'd better attack that instead of that chumb in armor" or whatever.
"Intimidating roar" is an interesting animal move. I wouldn't assume that a bear's roar would scare off a group of people—a dude or two, sure. But a big group? probably just draws their attention, which is useful, but dangerous as well.