Does the drop rate of chests depend on anything other than being present for the killing of the boss that drops the chest? For example, does the player with the actual kill shot get a better shot at a chest?

You only need to be present when the boss is killed.

Or, does the player that does most damage to the boss get the highest chance of receiving a better chest/better item?

No I don't think so. I saw player who never hit the boss got the locked.

Does the number of players attacking make the chest/item drop rate better or worse (i.e. would it be better or worse for me to solo the bosses myself?)?

It seems to me that only one player in the group would get the locked. I have never seen two or more players getting it. Hence, in a way, you can say it better to solo the boss.



This is based on my own experience of farming locked for ages. The most important thing is you need to have re-roll elixir, otherwise it is almost impossible to have locked dropped out. I have been playing for few months, and I saw the locked dropped only twice without re-roll.

The easiest way is to kill Jarl repeatedly, or Mother which could give you Ribbit as well.