I have heard this issue lean so many different ways it becomes ridiculous. Generally when the discussion focuses on threat per second I hear all sorts of mana-intensive abilities being used and when it leans to mana issues I always hear how somehow no abilities are really necessary to maintain aggro as a Paladin. If we're talking momentary AoE tanking and not main tanking, however, I could see using Greater Stoneshield Potion while unloading abilities.
Even with stoneshield potions while maintanking and somehow not losing threat, a Paladin still does not have a good solution for uncrushability and the lack of oh shit buttons remains apparent.