As you pointed out, RNG does play a role in raid gear. So it baffles me when people suggest that tomestone gear needs to be significantly lower in ilvl in relation to raid gear, when raiders themselves can benefit from tomestone gear when the rng doesn't favor them. You also touch on a significant factor of raiding. Incentive. While raiders have a number of incentives to raid, ilvl seems to be the only one given much credence... and apparently a 5 ilvl advantage isn't enough for many raider's egos.
Some raiders threw a hissy fit over the anima being able to get to 275 if I recall.