All I have to say is already said here:
Only change I'd love to see is to remove the target buttons and just allow you to click the players name to target them - seems more intuitive to me. Only just a minor change :^)
Icons for targeting are too small, and the header "Arena Master" is too big, just waste of space. Targeting through clicking on the name would be nice.
About the frame issue, couldnt there be an option for having the frame as big as nessecary from the beginning, as in: I know Im gonna do some 5v5 -> I chose "size 5v5"? Maybe, if it's possible, load that setting by itself if you can somehow detect which NvN arena you join.
I very often get in combat before I've seen all enemy players due to load and drawing distance.
I don't mind even making the frame size for 5v5 forever, with transparent background it is unimportant.
Also i had a bug recently when in 5v5 arena there appeared 6th member of opposite team, may be one from previous fight, i didnt remember.
And one more. The death of enemies almost everytime displayed incorrect. Usually they are shown as alive.