As seen here.
Does the dead personality's removal prevent the opponent from reacting with Assigning Blame?
Determination and Assigning Blame
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
As seen here.
Does the dead personality's removal prevent the opponent from reacting with Assigning Blame?
No.
Triggers, conditions, and leaving/entering play: "in triggers that involve a card leaving play, references to an in-play state of the card, such as its unit or location, refer to the state of the card before it left play."
Assigning Blame After one of your Personalities is destroyed...
Your When “your” and other possessive forms such as “the player’s” or “his” refer to a card, this means “controlled by that player" if the card is in play, or "owned by that player" if the card is not in play.
Assigning Blame requires that a Personality who was controlled by you before he left play has been destroyed. Things that happened after the destruction, such as removal from the game or reverting to another player's discard pile, are irrelevant.
On: Assigning Blame