As a Destro warlock, most of the time I use my Unending Resolve offensively to prevent other players to interrupt/silence me during my burst. However, every so often I after I use Unending Resolve and start casting Chaos Bolt I get interrupted. I tried to make a screenshot in duels with a friend, but was unable to reproduce it and I am too slow to screenshot it in Arena.
Unending Resolve does not guarantee your spells won’t get interrupted. DK’s will grip you, druids will push you, everything that makes you move cancels it.