Yes, it was "successful," insofar as he arranged a fatal injury for himself, which happened.
Since Harry lives, it wasn't successful, it was a failed attempt. You can be successful in taking a fatal dose of sleeping pills, but if I come upon you in time and your stomach is pumped out and you live,it wasn't successful. Harry arranged what he thought would be a fatal injury to himself, and believed it was fatal up until the time he woke up in Mab's arms on Demonreach. However Uriel and Mab had arranged it so it wouldn't be fatal, but that doesn't mean that it couldn't have been as Mab admitted, there were risks with Uriel's plan.. If she had her way, the shot would never have been fired in the first place and Harry would be suffering the effects of a huge ice cube being shoved in a most uncomfortable place.
If Harry hadn't had other interested parties get involved (without his knowledge or consent), Harry himself would have died.
That is true, but the truth is he couldn't hide what he was planning from an archangel and the Winter Queen. So they planned an intervention to stop him from killing himself. However Uriel is a bit wiser than Mab and realizing that merely stopping Harry from killing himself wouldn't be effective because Harry still believed as Winter Knight he'd be Mab's monster. So the Uriel version of "It's a Wonderful Life," Harry begins to realize some things, and Uriel's seven words had it's desired effect.
We know Ivy's involvement, there. And Mab, Uriel, Alfred after the fact... maybe before?
Of course before, Uriel, Mab, and maybe even Alfred, intervened. It was a close thing,and was meant to be a close thing between fatal and nearly fatal. Heart shot, not a head shot, falling into the ice cold water verses falling on the deck, falling into Mab's waiting arms verses just falling in the water to drown, life saving fluids from the island itself that kept Harry in a coma, alive, oh and last but not least, the "parasite" who would become Bonny agreeing to act as a heart lung machine
during all of this.
It makes me wonder, whether beings like Mab... like frikkin' Uriel! ... really left that moment up to "chance."
I don't believe they did, careful reading of what Mab said to Harry after he woke up says they didn't. She was still miffed at Uriel for taking such a chance with her Winter Knight in order to teach him a lesson, and I don't think it was his soul that she was worried about.
Rock the boat at the right moment... a few Pixies dragging Harry's shoulders... a Nixie or Neriad actually reaching on-board to grab him... Was there really ever any chance of "if he had fallen onto the deck"?
Not a chance in my opinion... And actually it fits with what Uriel said about "balance," Lasciel's words pushed Harry to suicide, so he was allowed to counter it. There are rules, even though in some religions the taking of one's own life is a mortal sin, angels, even archangels are not allowed to interfere with human free will. Lasciel's actions allowed Uriel to do just that, interfere with Harry's free will, he didn't allow Harry to kill himself.
Ivy forced Kincaid to make a chest shot and not a headshot. If Kincaid had done it with a headshot Harry would be DEAD dead. There wouldn't have been enough for Mab to save.
True, but why didn't Ivy just stop Kincaid from shooting Harry all together? I wouldn't be shocked if Uriel had something to do with that as well.