TankadinTPS is the mis-named addon which gives you fantastic in-game threat analysis, by ability. It knows DK threat.
Tiima posted results of some testing whilst discussing [item]glyph of disease[/item]. Tiima makes the point the glyph of disease gives more choice to the tank: do I need more threat or self-healing?
Kuren gives the change required to the addon to correct Icy Touch is to paste this into the ttpsDeathknight.lua file around line 54:
-- Icy Touch  = 7,