Support for Duo/Solo scaling.
The scaling should be representative of the DPS loss of going from 3 -> 2 or 2 -> 1 player(s), similar to how ToA and CoX work. In general, having more players just makes the raid easier for each individual because it lowers the burden per person anyway. Screwing up in a solo is much more punishing than in a party, and you can easily just be carried by your party.
Artificially inflating the difficulty by enforcing a minimum scaling gatekeeps players who may not have the time to find a group, players who are in the wrong time zone to reliably find a group, or those who may have no desire to run/find a group. This would be a big help for players that want to engage with ToB but are unable to due to their circumstance. There is a reason that the overwhelming majority of new content in OSRS is designed to support solo play as well as group scaling, especially in PvM.