May have something to do with this
https://us.battle.net/forums/en/wow/topic/20762318007
• UNIT_SPELLCAST_SUCCEEDED - no longer provide spell name and rank.
• UNIT_SPELLCAST_FAILED_QUIET - no longer provide spell name and rank.
• UNIT_SPELLCAST_INTERRUPTED - no longer provide spell name and rank.
• UNIT_SPELLCAST_START - no longer provide spell name and rank.
• UNIT_SPELLCAST_FAILED - no longer provide spell name and rank.
• UNIT_SPELLCAST_STOP - no longer provide spell name and rank.
• UNIT_SPELLCAST_DELAYED - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_START - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_UPDATE - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_STOP - no longer provide spell name and rank.
May have something to do with this
https://us.battle.net/forums/en/wow/topic/20762318007
• UNIT_SPELLCAST_SUCCEEDED - no longer provide spell name and rank.
• UNIT_SPELLCAST_FAILED_QUIET - no longer provide spell name and rank.
• UNIT_SPELLCAST_INTERRUPTED - no longer provide spell name and rank.
• UNIT_SPELLCAST_START - no longer provide spell name and rank.
• UNIT_SPELLCAST_FAILED - no longer provide spell name and rank.
• UNIT_SPELLCAST_STOP - no longer provide spell name and rank.
• UNIT_SPELLCAST_DELAYED - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_START - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_UPDATE - no longer provide spell name and rank.
• UNIT_SPELLCAST_CHANNEL_STOP - no longer provide spell name and rank.