From Dark and Darker Wiki
< Lich (elite) - 18.432% max unique weapon drop chance
That's not how probabilities work. P(A or B or C) = 1 - P(-A) × P(-B) × P(-C) So in your base case it would be: 1 - (1 - 0.016) ^ 3 = 1 - 0.984 ^ 3 = ~0.047 So 4.7%, just a bit less
Also, you're mixing in the Luck Vector when it's already counted in these simplified Loot Tables.
I'll update for HR in Patch 6.2#27: Rolls 3 times, 0.01 probability of unique. 0 luck: 1 - 0.99 ^ 3 = ~0.0297 50 luck: 1 - 0.9894 ^ 3 = ~0.0315 100 luck: 1 - 0.9892 ^ 3 = ~0.0321 150 luck: 1 - 0.9891 ^ 3 = ~0.0323 200 luck: 1 - 0.9890 ^ 3 = ~0.0326 250 luck: 1 - 0.9889 ^ 3 = ~0.0329 300 luck: 1 - 0.9889 ^ 3 = ~0.0329 350 luck: 1 - 0.9888 ^ 3 = ~0.0332 400 luck: 1 - 0.9888 ^ 3 = ~0.0332 450 luck: 1 - 0.9888 ^ 3 = ~0.0332 500 luck: 1 - 0.9888 ^ 3 = ~0.0332
So yeah... I don't know then, but currently luck doesn't affect this Drop Rate table's Luck Grades. It doesn't get better than 3.32% chance