I don't think that the corpse of Uther is under the Chapel because he got his tombs in the Western Plaguelands.
Uther's powers would not have been enough to stop Arthas after the prince became a Death Knight. His murder is an excellent example of that. After Arthas and Ner'zhul merged? Not a chance. And that was with Uther alive. Now that he's dead the powers of the Light permeating his body would have next to no effect. So there's no way that the body of Uther being present at Light's Hope Chapel would be able to defeat an entire Scourge army as well as severely weaken the Lich King.15:36, 4 February 2009 (UTC)
I think there's a holy weapon of some sort, even more powerful than Ashbringer, that they have reserved for its use in the final battle against Arthas, like the Holy bombs developed by the Scarlet Crusade with the help of the Naaru in Shattrath during the last Scourge invasion... but far more powerful. Orisai (talk) 20:14, 5 February 2009 (UTC)
I think Fordring more or less explains it during Battle for Light's Hope Chapel, that the chapel ostensibly uses the Scourge against itself, bending the pain of the enslaved spirits against themselves. The Lich King sends 1000 undead to Light's Hope, Fordring tells Morgraine that what he is feeling is the "agony of 1000 lost souls." It basically turns the Scourge's greatest strength into its greatest weakness. What exactly causes this is uncertain, although it is certainly related to the Light ("The Light will tear you apart Darion!"), which rules most powerful buried entities or objects, such as Old Gods and Titan relics, that are not associated with the faith of the Holy Light. But this is all speculation till we get some more lore on the Chapel, particularly its origins. Strength and Honour, Horderoyale (talk) 08:05, 9 February 2009 (UTC)