For me it's the difficulty of finding the right two individuals on my friends list on at the same time and willing to run trials (they tend to have their own groups already on the regular). I did manage to find a really good player on a LFG that was chill and another decent one the pulled us to the Lighthouse on our first card. I really just need one person that's better than me (this week I was rocking a 1.47 K+A/D on my titan and a 1.19 K/D on the same toon in decent to bad groups and found one person the same as me and one that was rocking 2-3 K+A/D and 2 K/D for as much as you can trust Destiny Tracker because it's not very accurate). I went on my hunter (gunslinger) and ended up getting 1.315 K/D & 6.64 K+A/D with my teammates getting 3.69 K/D & 9.77 K+A/D and 1.869 K/D & 6.14 K+A/D