Setup: BG2EE, no other mods installed other than SCS.
Rakshasa are still immune to "breach" even though I installed the "More consistent Breach spell" component (I'm getting "Spell Ineffective"). Specifically I'm referring to Ihtafeer, Saadat, and Jalaal. The console didn't mention any spell protections they cast that could have resulted in such behavior.
Also, I believe the above rakshasas grant far too little experience compared to the challenge they present (probably even when they are not immune to Breach) - these guys are immune to all spells lvl7 and below (your mage has to be lvl 16 just to touch them with a single spell), and by the time you've peeled off their combat defenses (assuming breach works and that you have at least 3 of them and can cast them uninterrupted - I've had very limited success with Inquisitor dispel) they have already bombarded your party with lethal AoE spells they are immune to (CloudKill, Fireball, skull trap, etc) - some of them can't even be dispelled (Web, Teleport Field).
If we compare the rakshasa encounter to others in the vicinity with similar XP IMHO the balance is severely upset, probably even with breach enabled. For example Bone Golem + 2 X Skeleton Warriors in the Temple Ruins is a complete walk in the park compared to that, and it grants more XP. The most reasonable thing to do here IMO would be to make Saadat and Jalaal some form of melee minions that are likely to aid Ihtafeer (golems?) rather than rakshasas (it would still be consistent with the quest, which only mentions one rakshasa as far as I recall). Another would be to change the room layout to something bigger with just one floor and more free space to maneuver - the way it is now, AoE kills your party and you have no where to run (running outside and waiting it out feels like cheese to me). Also, by the time you get through that narrow passage to the second floor with your warriors (and mage, to cast breach - twice!), the rakshasa above have already wreaked havoc - at the very least, make them spawn in the lower floor (adjacent to Ihtafeer).