It's like a lottery, the more tickets you by the better chance of winning supposedly. So likewise the more actions you have in the eb are suppose to increase your chances. But I've seen people with one unload on an eb get the item.
Missb is correct as the best way to increase your chance is to perform more actions. Ive never received an item even though I haves lot of actions. It can take a lot of ebs before you recieve the item. If you really want it you might have to do hundreds, of just one you never know.