I'm assuming this is the only katana available through normal gameplay in the 1.0 version. With that assumption in place, let's look at the weapon. It clearly states that it is "infused with solarium". However, it does less damage than a violium broadsword. I understand this is probably due to it dropping from an early boss. An easy solution to this problem is to learn a crafting recipe upon picking the weapon up. This recipe will be crafted at a separator table and it will allow you to apply more solarium. Which will make the weapon do at least as much damage as an end game crafted weapon. You could also switch the alternate ability from the kunai to the laser cannon on the upgraded version. People would probably like that.
You can run the mission again, you know. The drops scale up to you, depending on your gear (I believe, could be based on the highest tier planet you've been to). Once you have access to the Violium Broadsword you should be able to get the Tier 6 version of Solus.
I went to my separator tables, and sadly it was not there, was it removed, or do I have to farm the boss now?
Not when i have 6 solus after farming the boss for 3 hours And no it isnt as powerful even with that type of armor