Will this boss be multi or single combat? One thing I see mid level players ask often is "so what can I do with my friends?" And the answer is really quite little.
I also wonder if the 100 cb target is a little high? I think the game could use more stuff in the 85cb ish range, at 100 you start being able to access demonics/zulrah/vorkath. The mole/barrows bracket is quite a bit lower imo.
The intention is for the boss to be a solo challenge for players with around 80s combat stats (100 combat).
I feel like this is at roughly the point in the game where players get "bored" because they can't kill bosses yet but the xp to level up is getting noticeably bigger.