Coach qBaLLs :
Try and start your guild challenge an hour later maybe. You and your repetetive opponents probably start at more or less the same time and end up getting each other the whole time.
We had the same issue and changed our start time from evening to morning and since then haven't faced the same opponents twice going on about 3 weeks now.
How do you select a start time? If I request a search for an opponent, or leave it to the system it makes no difference.