People pull it out during others' hits because the hasta has defence bonuses, and pretty strong ones at that (+13). It helps soak up a little bit of extra damage in stakes.
The hasta is pretty useful during dds specs mainly due to the defence bonus it gives. Honestly though, it hasn't seemed to change much in terms of odds from the stakes I have seen.
Hasta has defence bounus so it will make weaker weapons (like dds) hit lower and more 0s. Since a dds spec is better than a whip hit its better to use it when your oponent specs.