Vajra and missiles act similarly in the fact that they are both tracking assists that can hit anywhere on the screen and can serve as another projectile that can fill the gaps in the soul fist spam. If you only use the assists for this purpose, yes they are redundant. But these assists are very versatile and can be called for many different situations, a number of which don’t overlap, which takes the label of redundancy and throws it out the window.
Vajra’s speed makes it far more applicable to a number of situations where the slower, multi-hitting, missiles would be inapplicable and vice versa.
For example: you are being pressured in the corner and pushblocking isn’t giving you the moment to breathe so you can enter fly mode and airdash a million times away or begin your own pressure. Calling Doom in that situation will probably result in his untimely end. Vajra on the other hand, has a much better chance of giving you the second you need to flee without sacking a character.
Hidden missiles, despite there name, are generally very conspicuous. When you press that assist button, you hear that noise of a missile firing 6 times, which to me sound like, “I’M COMING FOR YOU!!! AND WHEN I FIND YOU I AM GOING TO EXPLODE IN YOUR FACE!!” yelled in my face 6 times. After hearing that, I think “Ok, I’m either going to have to block soon, or move faster than they can track me” . REALLY good player’s will know about when “soon” is as they will have the timing for when HM should hit based off where the target is on screen. If used on its own, few player’s would have much trouble blocking or completely avoiding HM.
That said, HM is best used when you are ALREADY IN CONTROL and you want to keep it that way, be it filling the holes in soul spam, using the otg to continue a combo, etc. It excels as a continuing state assist
Vajra or the other hand, is far more effective as a tool to rapidly changing the current battle situation. As stated earlier, when you are being pressured, Vajra can help you quickly return to a distance where Morrigan has the advantage. When Storm is floating around in your air space, Vajra turns the Earth into Scorpion saying “Get over here!!” smacking her to the ground before she can unfly and block, which rapidly returns the higher ground advantage to Morrigan, where storm has to dodge more soul spam to get on Morri’s level. The speed and surprise can allow you to go from keep away to rush down in an instant. Example: you have backed into the corner shooting soul all over the screen, but the foe has gotten close enough that calling Doom can leave him open for punishment, but you still need to air dash over said foe so you have the rest of the screen to work with. You have the option to time Vajra so it hits around the time you are dashing over your foe, which will force them to ask “Is she calling the Ninja? If so, what side will she be on when he tries to give me a close up of his new Adidas? Will she continue that dash and play more of the lame game, or cancel into a shell kick and start rushing me down? If the later, what side is the shell kick coming from? Which will hit first, Vajra or shell kick?”
You can put the opponent in a similar situation with HM when it is safe to call them, but HM gives them time to think. Vajra doesn’t leave them with that kind of time. HM= identify, ponder, execute. Vajra= anticipate and react.
Vajra + HM is far from redundant. The main similarity they share is being two of the best assists in the game.