This is an counter-intuitive feature in the game: when near death and praying in temples, you receive pick axes and die. This is especially counter-intuitive in late-game temples, as the player most definitely has access to pickaxes and wands of digging (Darkforge's dwarven chaos knights).

The player must be able to rely on the resources he or she has (with certain limitations, such as teleportation). Lower prayer cost is a class power for priests, and they should be able to use it.

It is counter-intuitive that these resources function in a specific way 95 % of the time and in very limited circumstances, i.e. some of the toughest fights in the game, they suddenly change.

My suggestion is that when at low health in temples, you receive healing instead of pick axes and at high health you'd receive pick axes.

EDIT: It was actually grobblewobble's idea that you should get pickaxes only when nearly fully healed.