Instead of having initial raid placement when everyone joins be random, have it somehow factor gear donations into where everyone is initially placed.
Most high tier guilds have at least half the people solo Rancor and Tank, so where you end up placed is entirely random. Instead of having that placement be entirely random, maybe have it be based on the amount of daily gear donated or if not based strictly on it, have more gear donated give you a better chance of being ranked higher initially. Finishing higher in the raids gives you more gear, so you'll have more gear to donate and it will encourage people to donate more gear.
This would have little impact on the Sith raid, except for people posting 0s, but the people who post 0 with more donations will get better rewards than the people who post 0 with no donations.