Almost all the possible consequences of Quirrell's plot with Hermione might have helped Quirrellmort somehow:

• Hermione goes to Azkaban and Harry goes permanently Dark.
• Hermione goes to Azkaban and Harry goes permanently Light, killing himself to destroy it.
• Harry saves Hermione, further antagonizing Draco's father and thereby Draco himself.
• The wedge is driven further between Harry and Dumbledore.
• Harry looks very Dark in front of all of wizarding Britain, losing him Light allies.
• Harry looks very powerful in front of all of wizarding Britain, gaining him influence.
• Harry vows to wreak havoc on the entire wizarding nation.

The question is which set of events Quirrell most wanted to happen, and whether he will consider the events of Chapter 81 a success or a failure. Harry successfully saved Hermione, which might indicate failure if we take the plot at face value. But Quirrell would surely have foreseen Harry's going to any lengths to save Hermione, and Quirrell knows that Harry read that Rita Skeeter article. Perhaps he

The Harry-horcrux has a speaking part in Chapter 81, saying "DIE" when he looks at Dumbledore. If Quirrell's main goal was not to immediately rid Harry of all his strongest allies, but simply to further coax out Harry's Dark Side and further drive the wedge between Harry and Dumbledore, then he can count it as a success.

Maybe Quirrell didn't actually have one particular outcome in mind; maybe he just wanted to inch the pieces forward so he could plan his next move.

I do hope that tomorrow's chapter shows us what happened with Quirrell, how he got out of his interrogation without drawing attention, and what his mental state is about all this. If everything up to now has gone as planned, surely the rest of the arc will show Quirrell's attempt to make Harry believe that Dumbledore was behind it all. If everything has not gone as planned, if Quirrell did not expect to see Harry spend 250% of his fortune to save Hermione, then Quirrellmort will be pissed, and I shudder to think what his drastic next move might be.