try to add -w 3 or even -w 4
you could get even more speed with rules (but of course the overall runtime could increase too).
so the correct answer is:
1. more dedicated/clever attacks (specific to the target hash, better rules and dictionary, smaller is sometimes better )
2. more/better GPUs
update: wait you are cracking 18 bitcoin hashes. omg. that's also a reason for slower speed because of more salts !!! 17 unique of 18 total is also very strange, I would investigate this a little bit why 2 hashes have the same salt. that's not normal for bitcoin hashes, I guess
you could get even more speed with rules (but of course the overall runtime could increase too).
so the correct answer is:
1. more dedicated/clever attacks (specific to the target hash, better rules and dictionary, smaller is sometimes better )
2. more/better GPUs
update: wait you are cracking 18 bitcoin hashes. omg. that's also a reason for slower speed because of more salts !!! 17 unique of 18 total is also very strange, I would investigate this a little bit why 2 hashes have the same salt. that's not normal for bitcoin hashes, I guess