Cassius had been communing with a Fallen for Centuries, for all we know he had planned this in advance with a Fallen, in which case a Fallen Angel would equal an Angel of Death with surprise and mortal magic to sway the match, but Uriel is as powerful as Lucifer, his limitations prevent him from acting unless a Fallen is in play which Cassius did do.
Frankly Cassius didn’t think this out, he is hell bound and had he managed to have Harry shanghaied, who do you think he would have been assigned as a roommate?
An eternity of Harry cracking wise on his ass would make eternity especially long for Cassius. Uriel’s saved both Harry and Cassius.
I think the point you both are missing here is it was a piss poor curse to begin with. Sounds terrible but in reality didn't amount to much, that was what Malcolm explained to Harry..
repeat Dead Beat page 420
"Son. Everyone dies alone. that's what it is. It is a door. It's one person wide. When you go through it, you do it alone."His fingers squeezed me tight. "But it doesn't mean you've got to be alone before you go through that door. And believe me, you aren't alone on the other side."
I frowned and looked up at my father's image, searching his eyes."Really?"
He smiled and drew his finger in an X on his chest. "Cross my heart."
I looked away from him. "I did things. I made a deal I shouldn't have made. I crossed a line."
"I know," he said. "It only means what you decide it means."
Once Malcolm took the sting out of the curse, Harry wasn't afraid of it anymore, once that happened it became a non curse.. Yeah, at the end of Changes when he was shot through the heart and falling in the water he heard in his head Cassius cursing him, "die alone.." You can argue that he was only mostly dead when he fell into Mab's arms, but for 98% of Ghost Story Harry was convinced that he was all dead. Did you hear him complain once about having died alone? Did he seem to suffer from it? The answer is, no, he did not... Conclusion, piss poor meaningless curse. Even Murphy's death loses it's sting of you want to count that towards Harry "dying alone" because his true love died before him, heck, she is in Valhalla, one of Odin's soldiers now, so there is always the hope that he will see her again.. Or given what Malcolm said, she will be there for him when he dies someday.
Now Margaret's death curse on Lord Raith was a serious curse, the vamp cannot feed and has become an impotent figurehead... Now for someone like Lord Raith, that was a serious long term curse that has made him suffer.