This blade is honestly power-creep. It's a blade almost as strong as Thunderspine and WEB that isn't cursed, is gotten from a low-level boss and area, and is a lot easier and more reliable to farm.
It'd be a long post to explain things in full, but TL;DR if you don't have Thunderspine, and you don't have WEB, then you're better off having this weapon than either of them. There's absolutely no reason to go after any other weapon at this level; Black Shark Blade? Outclassed. Admiral's Cutlass? It takes a lot more effort to get and is weaker.
If the devs want new players to keep looting, they'll have to make new swords more and more powerful from level 30 bosses. It sets a precedent for how powerful they have to be. And because of this, they'll have to release more powerful weapons for level 40 bosses, and level 50 bosses, so on and so forth until we have insanely broken weapons for each level bracket and eventually we're stuck with a ton of overpowered blades that make the game less fun and engaging to play and make bosses and enemies even more dull to fight (what with them just being beefed up regular enemies with no exclusive skills that might make fights engaging and strategic).
Not to mention, the higher level legendaries are supposed to be something unique; an endgoal to look forward to. By making more overpowered legendaries available sooner, you effectively quash the wonder of getting those sweet, 90+ attack cursed blades with unique skills and abilities that make them a joy to use (this is another reason why jack's blade is unhealthy for the game; it fills the role of a healing tank that WEB fills and the role of a high-damage shredder that thunderspine fills without either of their downsides).