maybe it is just the matter of casting time, most mmo games have a non zero power casting time and they will queue if pressed in quick order. however since this MMO dont have an ability queue, it'll just interrupt each other.
we have a similar problem with champion online (the sister game, share the same engine), if you cast a power that have a long animation then quickly cast a spell with short animation, the short one will cancel the long one and the long one will not be casted. for example, try to cast BCR then follow it quickly with GIGABOLT.
Hotkeys are unreliable. I've submitted a bug report on it.
It's definitely a game problem, because I can often see a response from the client (i.e., the sweeping shader that moves across the icon when you activate a power) indicating the client has seen the keypress, yet the power doesn't actually activate.
It's bad enough in PvE, but in PvP it is a literally game-changing dynamic. Having to mash a button multiple times to make sure it "fires" is bad enough, that it also comes in addition to the need to mash Fire All Weapons to compensate for a byzantine set of weapon timers and multiple interrelated weapon exclusions impossible to manage in real time is inexcusable.
I recommend that anyone seeing this behavior submit a bug report in-game, because this is a very serious problem that needs prompt attention.
I noticed that too, I thought it might have been the target wandering out of the firing arc just as the torpedo was firing, and something might be preventing the launch if the target left the arc, but not the cooldown.