Before you open your vanguard package, make sure you have your highest light gear on.
Then equip a year one secondary before opening the package.
The smart loot system wants to 'fix' your lowest light piece of gear roughly 60% of the time, so by making your secondary the lowest piece of gear you're wearing, it will stack the odds in your favor.
I've done this 5 times and got a Longbow, Two to the Morgue twice, and an LDR from the Vanguard rep.
It sounds silly but it really works more than it doesn't.