It's quite hard to know where to start, but I'll do my best.
You sort of have the right idea, but you're a bit mixed up in places. I'll try to address the points.
A bunch of this stuff is hidden away (or not so hidden) on threads over at Maintankadin. I'd recommend browsing over there for a fuller picture.
- Stop taking Divinity. It's rubbish. It has no place in a MT build, never mind a heroics one.
- I promise it's possible to run heroics without OOMing in a standard MT spec, you just need to be a little careful and think about mana use. Wasting points in 2/2 SA, never mind 5/5 benediction and the Glyph of SA to boot, is a serious mistake. As long as you're tanking 3-4 mobs that are meleeing you you shouldn't struggle for mana, and your gear should be good enough that you barely need healing to do it meaning you're increasing the mana you gain via healing from nothing to twice nothing. Just remember to keep Divine Plea up.
- Redoubt is very strong coupled with SoComm and multiple mobs hitting you. Spec this.
- You want one point in Judgements of the Just. This makes judgements proc seals too (more cleaving goodness)
- Get Crusade. Skip vindication (nothing in a heroic can hurt you). Fill as many points in conviction as necessary to get crusade. Think about whether you want PoJ instead of two points in conviction (getting to next pack 15% faster is good)
- You can lose the second point in imp might (you need a point in something to get to next tier if you lose benediction(, it's a party buff (you need sanct on yourself) and it's hardly make-or-break for heroics.
- Get Redoubt. More damage to ShoR, and blocking is a huge part of your reducing damage taken in a heroic.