For spots where only a single class icon can be displayed (e.g. group bar) which icon is displayed for a multiclass ?

Is it the one with the most current levels ?

...that makes the most sense.

What if the levels are equal; e.g. if I have a 2/2 ranger/rogue, which icon is displayed ?

If I started rogue at level 1, but become 3/2 ranger/rogue do I then display the ranger icon ?