If you are fishing for a particular piece of legendary gear only available from loot packs, is it better to go with the Core loot pack to increase your chance of getting any Legendary piece of gear, or is it better to choose a [Faction] loot pack which - while having a lower chance of pulling a legendary - narrows the pool to increase the likelihood of getting the one you want?

In particular, I'm really craving a Solar Sustainer for my Ambra on my new account. When the game first released, I pulled one from a Jennerit pack, but the loot packs were structured differently than they now. I'm not sure if I should keep dumping my credits into Jennerit loot packs (which have all been extremely underwhelming so far except for her two best taunts) or if there's a better way now, so I'm all ears if anyone has any suggestions.