Assault warp is certainly overpowered and more than a little ridiculous. It combines monstrous damage with shield bypass and a warp, meaning that vettes that use it often don't need their other abilities to kill more fragile ships or those on low health; they just need to get up close and hit the 1 key and they get a kill.
Despite what the fellow above me alleges, it is more than possible for a corvette using this ability to get in close without burning his escapes. You do not need to use afterburners to get in the abilities usable range because there are navigation officer briefings that will suffice to get you close enough when used in conjunction with cover. Furthermore, since assault warp is itself a movement ability, it can be used as both initiation and escape simotanously; the damage it deals means firing other weapons is often unnecessary for its preferred targets, so it just has to warp through its target and then flee, burning its afterburners if it needs too.
As much as I loathe complaining about things being overpowered when there are ways to avoid them, In this case, awareness isn't remotely enough of a counter (IMHO) to dismiss the almighty power ABW grants to even a moderately competent captain. Pretty much every 'Vette has mobility and access to cover enough to close with an enemy relatively unmolested, even without the cloak - which is pretty much a crutch anyway. Then there's the Kreshnik, which scoffs at the notion of cover as it casually strolls towards you and melts your face.
The reality is, if an ABW vette wants to kill you, you're probably dead, no matter how much attention you give it as it approaches. This itself isn't necessarily an issue, as lots of other ships can YOLO into an entire team and take out a target if they prepare well (Ram/Storm missile Vindicta, for example) but they pretty much guarantee their own death doing it. A vette has a much higher chance of making it out alive. I've been in enough matches now where an ABW vette has been called out at pretty much every stage of it's attack run and has still managed to dump it's payload, delete it's target, and escape, or at least take up the entire focus of the entire team while it's escaping.
"But what about hard counters and status effects, Kiiyor?"
If you're close enough to Scramble, or Drain pulse, or Blast pulse, then it's close enough to ABW, and at close range, ABW is #1, everything else #2 or lower. If you try to dissuade it with disrupts, or missiles, it just needs to get to cover and wait, and then you're out of deterrents when it starts it's run.
Heck, even dreadnoughts are vulnerable to it, as shields are useless.
I've heard people say that if you position your team with lots of open ground between you and likely vette approach points, you're more likely to survive. I've also heard people say that having all your ships concentrate fire on the vette can work.
I'd say that If a single enemy forces an entire team to shift their tactics drastically to even hope to counter it, it's not balanced.
I think if you take away the shield pierce, it will be much more manageable.