Faction packages do not drop any higher than 330. It is true however that the level of drops (as in physical items that fall on the ground) isn't determined until you pick them up, giving you a chance to swap your gear around to max your level, but lowering your level isn't going to improve your chances of higher drops past 334. And i have ranked up enough of times and opened a lot of engrams to know how it all works :/ Elder sigil rewards and kings fall challenge drops are the only things that are correctly always dropping at 335 once you get to a high enough level.

That's what I've been doing. Save 334 gear and use it when expecting drops.