Redoubtable Blizzard poster Koraa comes to the rescue with words of reassurance: if rage/mana generation continues to be an issue with these spells (since they absorb damage and thus either prevent the tank from gaining rage via damage or mana via healing that damage) then there may well be changes to allow them to be less of a problem. We're warned that this would be a last resort fix, however.
I'd personally love it if a priest could shield me as I run in on a boss without being worried that I won't get enough initial rage to start generating threat. Perhaps (as some posters argue) the bosses will be hitting so fast that rage won't be an issue. We'll see what happens, of course, but the very idea of Power Word: Shield and its related talents not cheating me of my initial threat generation makes me giddy.