While I'm thinking of it, let me add the following, which are probably not entirely clear from the helpfile:

1) This is a short duration skill.
2) This is a reuse timer skill.
3) The timers for (1) and (2) are subject to change without warning once we get a chance to observe the skill in play a bit more.
4) This skill provides some damage reduction, but it is damage reduction that does not, as first grader report carts are wont to say, play well with others.
5) Above and beyond the reuse timer, there are frequently occuring conditions that will interfere with the use of the skill.

I wouldn't expect this to radically change hero assassin PK, and I especially wouldn't expect it to come into play in every fight, but it may make things more interesting.

Finally, I'd like to credit Cador for coming up with part of the base idea for this skill, what seems like a lifetime ago.