Some more:

• Sedna is still out of range but can get to you in five seconds.
• You are TB and you just used circle of fire.

QFT

any the above suggestion mean spending much money to even out big mistakes you made! at least for the very most situations. for the rare cases it would be really usefull it is not acceptable to allways spend that money just in case that.

no really, there are so much more usefull thngs you could do with the money that would be far more usefull and most times prevents you from needing the orb.

That said, my problem with it is that it occupies an extra slot in the inventory, so you'd have to give up something else.

for loking a portal and TP out safely without any interupt.

for consuming a robust potion in the middle of the battle.

Obscenitor uses it real well with Rook...

Seen it used well with UB cause ooze still works while you're stone...

All in all, just one of the few middle of the road items that don't suck but you shouldn't sacrifice upgrading your cit for.

But oh doesn't it feel good to turn to stone right when reg throws the mines at your feet right after a UB spit on you and you had a mark of the betrayer and the TB is about to fireball your ass and...

Yeah, I know... its not worth it but its a shame cause its a fun item.

It is the best item in the whole game. You can use it creatively in many cases, just because of that it is a special item that expands strategies of combos and the mind wars in group battles Few More points on top of what is already mentioned.

-To survive a spit.

-To spit and ooze damage.

-You can be healed by the monks as well.

-You can grab the pot or mana on the ground. 

-You can go next your towers and avoid a kamikaze kill. Espcially on battle on exp flag will be safe for you after defiance since you can get in and turn on invul.

-while you are under focus, the enemy spents few AA attacks and possibly skills if you time defiance right before they change target.

-It gives you few more seconds to do something in group battle which has vital importance to ahve the chance to use your skills once again even if you are gonna die. 

There are few other strategies with orb that i use but i will keep it as a secret to myself:)

Newsflash:  if any of your games are uploaded to replay, it isn't a secret anymore.

You can pick up pots while stoned If you're close enough at least.

Orb of Defiance is nice (you can stone on your/enemies portal and at least contest it), and it does give decent HP/Armor but I have a hard time with using it instead of a Sigil.