Warding rune doesn't change owner in castles, like all other runes do, including healing rune. I think it's because Warding rune was added from test after the runes had been changed on live, so, it was done before the change, and never fixed.
Also, Warding runes don't last long in non-save rooms. They usually get cleaned in a couple of minutes... Since it's biggest use is in hunting people (tracking movement), that makes it almost useless. it should at least always last the 12 minutes it's supposed to. THough, it really needs longer duration to be really useful... 24 minutes would make it actually worth it...
But it getting cleaned a minute after you cast it makes it... So worthless