Always a pleasure to get replies from you, Goa.
It is pretty underrated, the only real bad thing about is that I think only the duration increases with its level, the damage or healing it does is the same at all levels, thus not giving you much reason to advance it.
At level 3, this ability provides ten seconds of inaction -- pretty substantial for a capital ship. And its cooldown is next to nonexistent -- you can basically use this thing to either lock down or save multiple targets. It requires some micro, but rewards your micro immensely.
Because that doesn't take into account the antimatter the ability currently uses up. I rarely use marauders so I don't remember just how it works, but if you're using this as a quick retreat, you probably should disable group phase jumping anyways.
The antimatter cost is an issue, but if you provide an incentive to use Subversion, there you have a competing ability.
If implemented, a direct comparison to the Akkan Battlecruiser is actually possible:
Akkan:
- Colonize (used only on vacant planets)
- Ion bolt (circumstantial use: presence of critical targets that need to be interrupted)
- Aura (passive)
- Armistice (circumstantial use)
Marauder:
- Subversion (used only on occupied planets)
- Phase Out Hull (circumstantial use: presence of critical targets that need to be interrupted or phased out)
- Aura (passive)
- Phase Gate (circumstantial use)
If it is a sabotage team why would they disappear when the marauder leaves?
Because if they didn't they'd last forever? 
Incidentally, I find the ability icon, which invokes images of Vasari ninjas, highly amusing.
On a more serious note: we'll assume that the Vasari strike teams are too valuable and highly trained to throw away; hence, the Marauder retrieves them before it leaves the system. But this IS an oversight, because you can hardly expect a Marauder to remain in a system for 5 minutes!
Embargo barely affects trade centers and refineries. It only keeps the trade ships from moving, but the owner will still get income from them until they are destroyed. Its main influence is on tax income, since 30/60/100% of tax income gets transferred to you, which is even better than reducing its income.
D'oh!
I had completely forgotten that Embargo stole planetary income (it's been a while since I used it).
I'll have to revise my suggestion based on a comparison with Embargo.
Thanks for catching that, Goa.