That will remove UA without getting the damage, same with COS.
When I had UA it did about 3-4k when dispelled. It's hard to track because the damage gets counted as the dispeler's damage. A priest friend of mine just shields himself and rolls the dice with his dispels as long as he is not being focus fired.
@Ignayshus: I'm not talking about bubbling out of UA that is on the Paladin. How viable would bubbling and dispelling a partner's UA be? After the UA is gone, your Priest can easily wipe all the other debuffs in a few casts while you heal up in bubble.
None of the mob dispels in general will proc UA (shadow labs channelers for instance). It might be an oversight on blizzards part by not marking the felhunter dispel to trigger UA or that UA itself is coded such that it won't work against a non-PC in general. However, even if it did work against a felhunter, odds are pretty good that it would get a decent partial resist with all of it's natural resistence to magic (140-238? depending on spec) and the silence is shorter then the cooldown for devour magic as well.
Paladins can divine shield themselves and remove UA without taking damage or silence because they're immune to everything but mass dispel.
Is it a commonly used strategy? I don't think it's super common, it really depends on the situation. Healing is rarely the same fight to fight. Warlocks with UA tend to be pretty squishy, so do what you will with that.
Paladins can only dispel 1 magic debuff at a time and affliction warlocks have a dispel resist talent IIRC. The player is probably going to have 3-4 dots including UA so bubbling specifically to counter UA probably isn't worthwhile. You might as well be cleansing if you happened to be bubbled for some other reason and no one needs immediate spam healing though.
You can bubble out of silence, you can't bubble out of a locked spell tree. IE: I'm casting and I get hit by counterspell, I can't bubble; A priest's "silence" skill, or improved CS when I'm not casting can be bubbled through.