With two healers it's very manageable and it's mostly used in savage and you're prepped for it with a Bene. Outside savage WHMs can heal a DK out of walking dead if they get good crits or if they have PoM up as a defensive CD. AST probably has it easier as a single healer if you're not counting Bene because they have a 40% heal increase with ED, still takes like 3-4 GCDs but it's definitely better than SCH or a WHM without a Bene. I've personally never had to heal someone out of walking dead with only temperance so no comment there.