Frankly, the katy creeping barrage has no real merit to show aside from taking up the vet1 slot.
What I would propose is something as simple as removing its muni cost and making the barrage area smaller, or by keeping its cost and increasing the number of rockets fired.
Another alternative would be to increase the number of rockets fired in each salvo. The Katy would be much more effective if it fired 2 salvos of six instead of 3 salvos of four. That's one reason why the panzerwerfer is so much more effective in some situations, because its rockets are all fired at once/in rapid succession.