It's also a viable weapon to stuff in the grid just in case you pick up a phantom spear and you want to use it for your water team. Granted, that in itself is a stretch between the odds of picking up a phantom weapon and how few SSR water spears there are.

The weapon skill effect page putting crits in the same multiplier as berserk's pretty old. Like I remember that being the understanding last year.
Going through the history for the damage calculation page, it's the June 13 edit this year that put crits into their own multiplier. For that matter, the July 28 edit starts separating vigor from special (but still labeled both as special). The August 20 edit fully separates vigor from special.