I've had the issue of maps not loading fully or the UI for multiplayer not loading. It be nice if Bioware fixed these problems.
At first, I thought it was my computer, but it only occurs with some maps. At a certain point it hasn't loaded whether its the rest of the map [so I'm stuck with 'canyons' or the enemies don't load].
There is a map issue that the community facetiously refers to as "Narnia," which is probably what you're describing. Most of the map's features don't load properly, and it is generally impossible to move around or interact with enemies or teammates when it happens. Your teammates are not necessarily experiencing the bug at the same time, as sometimes they can finish the mission without you, or even pull you to them causing the map to load properly when they open the door to a new area.
I don't know what factors cause the issue to happen more often or less often, but everyone experiences it from time to time. It is generally a fairly rare issue, in my experience, but I may be subject to fewer of the factors that can cause the issue (and I suspect connection plays a role - mine is pretty good.)
It does happen with all maps. There are only three (not counting the DLC that was just released) but I don't know if some experience the issue more than others.
And any dialogue should appear at the bottom of the screen or we should have the option to change it. I don't believe there is a option to customize it, but it would be nice to change the size and thickness of the lettering and where it goes.
I believe that PC players had the option to customize text size added in one of the patches. 5 or 6, I think. I played it on console, so I wouldn't know where the option is, specifically, but check under the graphics settings, you might find something there.