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I subscribe to the school of writers who like to (and often must), outline their stories before writing them. For a long time however, I did not use the 3-act structure. My mentality on that has now changed, and I find myself playing catch up. 

One part in particular of the 3-act structure has me somewhat stumped, and I was hoping for some help on it: the second act. 

I'm very much someone who needs clear steps. The first and third acts have these steps, and it's easy to build these acts as a result. The second act does not. The most I've been able to get in the way of steps is as follows: 

 - Character reacts to Point of no Return. 
 - Unclear 'phase' in which the character continues to react. 
 - Midpoint, which starts the character acting to win, rather than reacting to survive. 
 - Second unclear 'phase' in which the character continues to act. 
 - Darkest Moment, where the character fails. 

Everything after the darkest moment is perfectly clear to me. It's those two phases which I have trouble with. I understand that they are there to bridge the gap to the Midpoint first, and then the Darkest Moment (usually preceded by a seeming victory). But I'm not seeing them as needed. Why can't the outline be as follows: 

 - Point of No Return. 
 - Character reacts to Point of No Return, struggling to survive. 
 - Midpoint. 
 - Character acts to win against the antagonistic force. 
 - Seeming victory
 - Failure, leading to darkest moment. 

That makes sense to me, but everything I've seen says that the second act comprises roughly 50% of your story, and that the reaction and action before and after the midpoint are super stretched out. Why do they need to be so long?