Res'ing is weird in it's rules and LoS. As for the action of res'ing, it's not a problem, you go out of combat after so many seconds, so res'ing is perfectly fine. On the counter to it, you could always have gone and melee'd the caster. (I know it would most likely been instant death, but still that's not the point.)

For the defense, just wait them out. Sooner or later they'll come to you. Go make yourself a sandwich or something if you're tired of waiting.