I said use Seal of Wisdom when during the when you dps during a fight as a tank. Spiritual Attunement and Sanc wont help you unless you are taking direct damage. And this is something to think about if you do get mana issues.If you have divine plea, 1/2 sa and Sanctuary on, you just won't get low on mana unless you grossly overgear the fight(as in, t10 against ONE enemy in a heroic instance). And if that is the case, you're much more likely going to be able to manage just fine by, say, dropping consecration.
Im speaking from raid experience for Heroics just pull more groups and use Avenging Wrath to make Consecrate draw more aggro. Tab around to see if they are/arent assisting find their target taunt it to you and attack it.