The Spirit Realm

Clamford's right. This AA wouldn't do anything but make sure LoH gets used. You aren't going to be healing any clerics or warriors with your LoH if you're DEAD! This AA would just make sure you don't die with LoH up. That's all it would accomplish. If you want to use it on a cleric or warrior or anyone else, you certainly could, but if you take lethal damage, your LoH would trigger on you.

Check the posts made when Nodyin was asking about pally AA suggestions. An AA that does exactly what you're talking about was mentioned and submited to him for consideration.

How about Paladin get an AA:

Blessed (or something): Duration 36. Blocks DI (to stop stackign issues). If reaches 10% of life (or something) Lay on hands has a chance to trigger on self (if avalible).

SK's get something like:
Vengeance: HT now triggers a 36 min duration buff on self which acts as a DI varient. In essence they HT the victim take their HP and store them as a DI style buffer (for how it works logic). Game mechanics it's just a DI if they used HT in the last 36 min.

Both have advantages, and disadvantages.

Son of

Maybe their harmtouch can fire on a mortal blow on the mob that killed them.