Blackout can really suck if you are caught in the middle of it...
Also, I agree with wheel and will take it a step further. Any build that cannot function without one of its skills needs to be reworked. You need to be able to lose some and still be able to function.
On the same vein of thought, you should never build a skill set with the assumption that it will work against subpar enemies (unless you are making a PvE build

). If it only works against idiots, doesn't that make you the bigger idiot for using it? You knew it was a crappy build and ran it anyway?
So...if you use IW as primary damage, make sure it is well covered (at least one enchant, but more would be better - like IoW and IoH). Also make sure that you have some way to protect yourself or you are dead before you start, distort works well (please don't heal sig while you are getting beat on unless you are also under distort).
If you use IW as supplementary damage (I think I am the only person who does this) then ONLY use it as supplementary, don't run out in front and start wailing on people...
EDIT:
Wheel, your last post slipped in while I was writing. I totally agree. I think it is a bad skill to use in PvP, and as with any one-trick-wonder builds it is much easier to counter than it is to maintain.