Cantha characters in Tyria

Ok, I'm getting pissed off at a-net. What's the point of being able to go to Tyria with an assassin if u can't do all of the missions? It's not like I'd be overpowered, because Tyria characters at lv20 can do those missions. This just prevents me from getting the tyria mission award. This is stupid. I've ascended and got to RoF alright, but I cannot play Borlis pass or the first level.
A-net needs to do something about this, cause we will all be tired of cantha soon, and there;s nothing for us to do in Tyria.

I'm similarly annoyed in the other direction, I want my Tyrian characters to do the early Cantha missions. Why shouldn't we be able to get the Protector title for both continents?