[quote name='Ski Hawk']Well, I'm trying to catch Giratina right now, and obviously it's a bitch. I have him paralyzed and down to a few HP (I know I could get it down a sliver more, but I don't want to risk it). I like paralyzing legendaries since it's permanent, unlike sleep and freeze. I know it'll be tough, though. In diamond, it took me 3 trips and over 200 ultra balls to catch him. Haven't gotten more than one shake yet.[/quote]
When I caught Palkia in Pearl, I finally ended up catching it with full health. I saved right before I started the battle and only had about 20 Ultra balls, so when I ran out I just had to restart. After about the 3rd or 4th restart, I just starting throwing ultra balls on a whim - caught it on about the second one thrown.
I think the game just operates on a percentage chance for the legendaries, regardless of how you have their health. Although I could be completely wrong, it's worth a shot.
I finally picked this up last night after one of the Walmarts around me was completely sold out. Next is that behemoth of a guide I am going to need.