Isn't it a problem that they can go there multiple times?

Invisibility is also needed to deliver an unreturned strike, not just to sit there.

I've already checked and written about it.

No, no mass dark spells affect invisible units. Only chaos, but there aren't that many of them, and not that many races worth fearing.

There's no need to exaggerate their ability and turn it into something incredibly overpowered. They probably won't even pay much attention to their owners, so setting a single goal to detect them at all costs is pointless. They will try if possible, but not necessarily.

Yes, they WALK there, but during this time, the Mistresses could shoot.

An unreturned strike once is not very effective; they will quickly target and eliminate them.

I know... sorry... I just realized it was too late the second after I wrote it. But I didn't delete it anyway, I was just too lazy. :)

Why don't they work? Was that also checked? And as for chaos spells... since removing invisibility by killing with chaos isn't that important, then chaos isn't a priority either.

And no one is calling them cheaters; I'm just saying that anyone can easily deal with invisibility if they want to.