I'm enjoying rangers but one mark on me and assassins can see me forever
Until they switch mark or I log out. That basically nullifies rangers most powerful move. Maybe a day timer? After that time you cannot see them anymore

Just a thought.

Across the entire spectrum of classes and cabals you will occasionally find abilities that seem like they completely shut down a particular build or class, and sometimes they come very close. The aspect that maintains balance in those scenarios is the variety and the fact that the assassin has weaknesses too, even if they aren't necessarily ones a ranger can exploit, and eventually he's going to feel the pain of those weaknesses. And of course you're welcome to use his perceived advantage against him by luring him into a trap, for example.

In your specific case, it might be worth asking yourself: can I beat this guy at all? If yes, try going on the offensive. If not, it's probably time to choose between ganging him down or running and hiding. And remember, as a ranger you should have the upper hand on the running part even if mark makes it difficult to hide, and if your pursuer has to essentially start over in looking for you every time he runs out of movement chasing you then that's to your advantage as well.

Sometimes CF seems like rock versus paper when it isn't, or at least it doesn't have to be if you don't let it.

You really need to be wary of them and those revelation shamans. There are much more people around to mess with.

I would support a timer but much longer than a day. Maybe 400 hours.

Because it sounds totally unreasonable.

Too short. Or too long?

You didn't state reasons, so I wonder.