Change Legendary chance to pseudorandom

[Green_Dragon]

I have a few concerns regarding pseudo randomness. The idea Coconut provided is easily exploitable (also brought up by Thunderstorm, I think); a player can simply boost his legendary change by spamming a ton of normal runs and switch to only doing ragnarok to ensure the best possible loot, by joining wave 12, going to spectator and join back once Odin is the last one alive.

As suggested before it should be certain boss waves that count. Like: Boss killed-->No Loot-->Increased Loot Chance.
How do you spam Normal Runs with people joining at least on wave 12. It takes you time to get there. Time most people
don't have or don't have the patience for. Only bosses that actually drop should be effectively increasing the pity rate.

Wouldn't it even be possible, if not achievable otherwise, to exclude Normal completely? Making the first boss to be effective
6 Hard would be more than sufficient, wouldn't it?! Also: Can you imagine the shitstorm for someone staying in spec until
Odin in wave 15? I think you should trust in this case the immense group pressure that would be put on an individual that
tries this stunt.