Ha, I had the same experience; Saw the Pillars and went "These must strengthen Raphael in some way and must be destroyed. How they buff him exactly, ¯\_(?)_/¯."
IIRC, it wasn't until later during testing that I noticed he got more Soul Charges after I destroyed a Pillar (I guess thats what they were counting on people doing, otherwise it really is wonky/badly designed).
Although, technically, Raphael is the most optional boss of Act 3 (Barring the fact that 95% of Act 3 is optional), because, atleast on a first blind playthrough, you can just accept his deal and not know about HoH at all.
The organic way of discovering is either through Shadowhearts quest or ransacking the Devil's Fee.
And we are talking about Honor Mode, where concerns about accessibility shouldn't exist (because you know what your mostly getting into) and the devs should be throwing their hardest version at us, and even then, you technically don't need to fight him to finish the game on Honor.
And also, to his credit, he probably is the hardest (or, personally, the 2nd hardest behind Ansur) but even then, Larian did make it much easier by giving out a healbot (Hope) and infinite Long Rests.
Also, apparently, in Patch 3, they made Raphael CC-able (along with "Inevitable Resolve").
Atleast Hotfit 17's out so I can continue my Honor run and see how the fight is.
On a separate note, I kinda see him as Flemeth from DAO; A very hard optional fight that offers strong rewards and the best ending for your character(s) (Although, the Hammer doesn't fundementally change the ending so ¯\_(?)_/¯)
