Self-revive takes several seconds to complete. After those several seconds, he starts standing up. He can be killed at that moment. Phoenix gets nothing except 60 second cooldown.
Proposal: The moment self-revive goes on cooldown, he should get a few seconds of revive shield.
Also, if Phoenix is charging Healing Pulse and switches weapon, he gets no benefit but still suffers from cooldown. But a fragger can pull out the pin from the grenade, and safely put it back.