To elaborate since my sentence seems poorly worded; I actually never took a step once into ACT 3 until Honour Mode so my entire run of ACT 3 was a completely blind first-attempt, not just Raphael. Honour Mode for me is just an excuse to experience the story's evil choices for which I'm not overly attached to because I can't properly experience the story's intricacies this way, so that's why my first ever ACT 3 experience was on Honour Mode and this was my first ever fight against him. My actual 1000 hours of playthroughs only ever go to ACT 2's finale and are waiting for Larian to polish all the ACT 3 story elements so I can properly experience the story (and naturally to optimize the act so it doesn't run like utter dog shit) 
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Wow. That was quite a choice, and probably too much fate in Larian. Nevertheless, after 1000 hours there is little possibility of encountering anything challenging.
My first blind attempt was quite exciting. I've made the mistake of taking out the pillars to which he responded by going hyper-mode and nuking half of my party and Hope to death. The fact that it is better to ignore the obvious pillars suggests a wonky design choice.
The main issue is that Raphael is hyped up to be a near godlike creature, but in the fight he is nothing special. A regular enemy with an unusually large health pool. Grym is a far more imposing foe, especially for the level you usually encounter it. Raphael needs to be somewhat easily beatable if the player is locked into the House of Hope following a main/companion quest.
I would have made Raphael a highly optional challenge, where the player has to explicitly choose to attack him.
An example of a great boss fight is the demi-lich encounter in BG2. It is just a single floating skull that casts Imprisonment and is immune to control spells and weapons bellow +4. There are a few (once you know, easy) tricks to kill it, but the first try is bound to be a shocking experience. This is how it should be. If you get into a fight with a creature way above your power levels, you should need to find some kind of "trick" to kill it. The usual strategy of disable + hit hard shouldn't work.
