I don't think I've ever gotten anything from the court above 280, a 276 ghost shell has been the highest drop for me so far. It's hard/rare finding anything 295 or higher in regular gameplay too. I think Nightfall, Iron Banner, Trails and King's Fall are about the only ways to get 300+ gear from what I know at least. I know how you feel, I stayed stuck at 295-297 on my Hunter for the longest time. I was able to get him to 301 after the January Iron Banner (first real PvP gameplay for me). After that I started getting some 310 exotic drops which I've been slowly infusing to get him higher, a whopping 306 now. It can be daunting but you just got to keep pushing.