this servant is bugged. it is not consuming its hp with each attack, also just attack 2 times. it should attack at least 3 times. if you heal it up, even more attacks possible.
please also check noble energy. maybe the same issue.
ok the mouseover is just wrong, it loses hp, but only attacks 2 times. it should be 3. after the second attack it channels another attack but dies before using it
Fixed. Your Holy Servant now makes its three attacks. It always had the health for three: each attack costs it 300 of its 810 HP, and the third one uses up the rest. But it disappeared at the moment it paid for that third attack, before the attack was shown, so you saw it start casting and vanish. Now the third attack lands and the servant goes a moment later. Healing it still buys more: heal it for about 100 HP or more before its third attack and it makes a fourth before its time runs out, and the end of its time no longer cuts an attack off halfway. Its health bar now goes down with each attack, so the mouseover shows what it has left. Noble Energy had the same problem with its last attack and now makes all four of its attacks. Live after the next server update.