Literally the only skill that does actual damage can BARELY hit 3 maybe 4 enemies if you're lucky if you're not reforged. For an AoE, that is pathetic.
My lv 20 hits pretty much everything that spawns, there is 0 comparison to be made, that one single reforge is the entire make-or-break thing that holds ninja back or lifts it to greatness. You can tell how important it is just by taking a look around and seeing how ninja is so lowly regarded or seen as utility, as no one has any experience with the reforge and if they had it their minds would be blown. No other skill has this kind of mechanical dependency on a reforge to such a degree.
Besides, you can't properly do the relentless room-wide AoE barrage of destruction that is guns+ninja if you don't have the reforge.
The talent still gives you access to Sakura Abyss and to a lesser extent, instant-throw charging shuriken. Kunai Storm might have lackluster range but it hits harder than Crash Shot, Shooting Rush, and Windmill (on ele-immune). Plus it has great momentum and doesn't cause enemies to agro you instantly.
The most effective strategy for clearing trash content (anything below lords) might be the combination of Shooting Rush and Kunai Storm but I don't think losing that reforge knocks it down to the same level as martial arts. Granted, it's a good reforge (more than doubling the area of effect) but even without it Kunai Storm covers only 7% less range than Shooting Rush and it's not like you've made its width reforge mandatory.