Bronzewood Capital Group

If you kill Yama solo, the odds of getting any Oplate piece are 1 in 200, or 1 in 600 for a specific piece. Using the coupon collector problem, we can calculate the expected KC to RuneScape gold complete a full set:

Average KC=200×3×1.83≈1,100

Average KC=200×3×1.83≈1,100

So, purely from direct drops, you'd expect to complete your Oplate set after around 1,100 solo kills.

In a duo, your drop rates scale with your damage contribution. Doing 50% of the damage reduces your odds to 1 in 400 (or 1 in 1,200 for a specific piece). Doing 60% of the damage improves this slightly to 1 in 333.

Time Analysis

Assuming a melee setup:

Solo kill: 6 minutes

Duo kill: 3 minutes

At these rates, the total grind time to complete a full Oplate set is approximately:

Solo: 110 hours (1,100 KC)

Duo 50% damage: 110 hours (2,200 KC)

Duo 60% damage: 91.8 hours (1,800 KC)

This shows that unless your damage contribution is significantly higher than your partner's, soloing or duoing Yama results in roughly the same total grind time.

Forgotten Lockbox Impact

The Forgotten Lockbox changes the dynamics. Each kill grants a 1 in 33 chance at a lockbox, regardless of your damage contribution. Within the lockbox, there is a 3 in 43 chance of obtaining any Oplate piece. This gives an overall 1 in 4,433 chance per kill for Oplate from the lockbox.

While that seems low, it actually improves the drop rate slightly:

Solo: from 1 in 200 → 1 in 191

Duo 50% damage: slightly better because the lockbox ignores contribution

With the lockbox considered, duoing can actually become slightly more efficient than soloing, as your odds from the lockbox are unaffected by shared damage.

Oplate Shards: Dry Protection

Without Oplate shards, a large portion of buy RS gold players can go thousands of KC without completing a full set. Including shards drastically reduces this grind.