His intent may have been the same in the disguise and out of it, but certainly, he manipulated people even more shamelessly by abusing the privileges of his disguise.
And here, he also abuses the privilege of his knowledge, telling Isabella again that her brother is dead, and having her be sorrowful in front of the crowd.
He does this for no reason other to have her be very happy, and perhaps look even more just and heroic, when it is revealed that he actually saved Claudio's life.
The Duke did his duty as a ruler, seeing to it that justice was kept and no undue sentence performed; however, through this public performance of accusation, repentance, and grief, he shows the extent of his power, and makes himself look even more just, important, and beneficent since he appears to have single-handedly acquired justice for everyone.
The theme of justice is also apparent, as Angelo will have to judge his own guilt here, as the Duke says he should.
However, Angelo has become no more just than he ever was, and has not learned of moderation in justice either; he tries to cover up his wrongs by trying to silence justice, which luckily, he does not get away with.
The Duke is still coming off a little like Prospero, making himself seem a benevolent advocate for Isabella, and one who used his power rightly, even when he was in disguise.
But, though the Duke says he did "not [change] heart with habit," he did abuse his disguise as a priest to get people to trust him and believe in his unproven honor.
One ironic note, though, is that Angelo senses that the two women are "but instruments of some more mightier member"; in fact, they are playing the parts the Duke has set out for them, and this will soon be revealed to all.
Angelo's repentance seems a bit abrupt, especially his statement that he deserves to die for what he has done.