I raid 25m only and I have received 0 loot from 2 resets while being the highest on dkp from day 1. On the other hand, I see people in 10m getting 4-5 pieces of gear already. The biggest factor is of course, the damn RNG. On 25m, there seems to be a tendency of the bosses dropping 2-3 of the same item that people don't even want. And even if what I wanted did drop, there's much more competition to get the gear than if I were in a 10m raid. The items not dropping mean they're gonna get more expensive and the fact that you have high dkp is no longer an advantage.