I've noticed this off-and-on on one account over the past few months, and now on another account I had this all evening.
When looking for a match I'm presented with nothing but low resource opponents, mostly 4 figure resources although some are low 5 figures. This is at odds with the resource levels I'm usually presented with, and I'm not even sure if the resource figure is accurate. They could well have more but that's all I'm able to loot.
Is this a known issue and I should just grin and bear it?