The low-health shield does not stack with Frozen Turtle Shell, and the team damage redirection effect does not stack with the Paladin's Shield or the Hero Shield.
When the player's health is between 25% and 50%, they both give the Paladin's Shield buff to nearby teammates and get the Ice Barrier buff at the same time.
Although technically available later in the game than the Ankh Shield, the Frozen Shield is a great alternative because of its defensive abilities and much simpler crafting tree, especially if debuff resistance is not necessary.
The Frozen Shield can be considered more effective than the Ankh Shield during single-player boss fights, given that most boss encounters do not cause debuffs that can be prevented by the Ankh Shield, and the Paladin's Shield effect will not cause the player to take increased damage.
With the Warding modifier, the Frozen Shield has 10 defense and a 25% damage reduction when the player is below 50% health, making it an extraordinarily strong defense accessory in single-player.