It's pure RNG if the OP is referring to drops. In past dungeons we used to laugh at all the useless gear that no one needed that dropped, ie. Pali loot when there is none in group. I believe BW has changed that to some degree in the FPs, but in random world drops it seems to often be something you don't need.
For me since I'm currently leveling a SI it's always str gear. I will give kudos to the game for trying recently. During my final Bonus Quest on Taris I had three identical pairs of green light armor int gloves drop. But of course I already had a pair of nice orange ones. When I'm on my Guardian it will be dps str gear. /sigh
On the other hand I'm amazed at all the purple drops a couple of my characters get. Usually nothing I need but at least I can sell them.