The ring could have been destroyed a lot easier.

[Celuien]

Originally Posted by The Sixth Wizard

What are the limitations he is subject to anyway, I can't remember where I read them... I was under the impression he has to be limited to the incarnate body...

The Valar barred the Istari from open displays of their full powers when they were sent to Middle-earth.

Originally Posted by Unfinished Tales, The Istari

For with the consent of Eru they [the Valar] sent members of their own high order, but clad in bodies of as of Men, real and not feigned, but subject to the fears and pains and weariness of earth, able to hunger and thirst and be slain; though because of their noble spirits they did not die, and aged only by the cares and labours of many long years. And this the Valar did, desiring to amend the errors of old, especially that they had attempted to guard and seclude the Eldar by their own might and glory fully revealed; whereas now their emissaries were forbidden to reveal themselves in forms of majesty, or to seek to rule the wills of Men and Elves by open display of power, but coming in shapes weak and humble were bidden to advise and persuade Men and Elves to good, and to seek to unite in love and understanding all those whom Sauron, should he come again, would endeavour to dominate and corrupt. (emphasis mine)

Hope that answers the question.