Imp LoH vs Touched by light

So I have come up with a build I haven't seen posted on this forum or other sites.
12/53/6
http://www.wowhead.com/?talent=sVcbMZ0xVAcuMtehRGoxo
build for survival, not threat.

It has imp LoH, traded in for Touched by light.
With Imp LoH I gain 50% bonus armour for 15 sec.
Is it worth to lose the spelldmg for it?

The big question is:
How much threat do I actualy lose by this, and how much survival time do I get from imp Loh if the "oh shit" situation occurs?

I want some evul math genius to calculate this, assuming the pala to be pre-nax-but-ready-for-nax geared.

Thanks in beforehand
_________________

It really isn't worth the loss of free spellpower.

I'm afraid with the seals nerf weakening SotP, pretty much any points in Holy is wasted for Prot.
_________________
Blog


Do you use your powers for Good, or for Awesome?