The Zeal cleric capstone Blaze of Glory reads as follows:
When you are reduced to 0 hit points by an attacker you can see, even if you would be killed outright, you can use your reaction to move up to your speed toward the attacker and make one melee weapon attack against it, as long as the movement brings it within your reach. You make this attack with advantage. If the attack hits, the creature takes an extra 5d10 fire damage and an extra 5d10 damage of the weapon's type. You then fall unconscious and begin making death saving throws as normal, or you die if the damage you took would have killed you outright.
The Dhampir has a natural weapon bite attack (1d4) that can be empowered to heal them for the piercing damage dealt by the attack (or give them a bonus to their next attack).
Hypothetically, using an empowered bite for your blaze of glory would then result in you being healed 1d4+5d10 (no additional damage from divine strike, since it's not your turn that you're making the attack on), while the blaze of glory renders you unconscious, since there's no conditional mitigating of that clause for healing above 0 hit points.
Does RAW result in the silly situation of a PC getting lots of healing from their attack but still collapsing unconscious as though they had ended their action at 0 HP? Are you conscious but fall prone? Does the healing above 0 HP prevent death from an attack that would have otherwise killed you outright, since that effect is stalled until after the healing?
Presumably there's no death saving throws since you've been healed/stabilized "as normal."