KarinsDad said:
It depends. What if the BBEG is a fighter type? Do you give him a Cloak of Major Displacement knowing that the PCs will probably acquire said item? There are not that many items that significantly protect against Orbs and which a DM might want fall into the PC's hands.
Or do you give him a Wizard cohort with instructions: "I know that Bob likes to use Orb of Force, so cast Displacement on me first round."? Sounds kind of railroady (wish I had a better non-existent word for that

).
Those are some options. Of course, the DM has free reign, so if he REALLY wanted to, he could just say that he is immune or has energy resistance against that particular spell. He doesn't have to explain WHY or HOW this particular BBEG is being unaffected (or less affected) by the spells. Perhaps a Wizard cohort buffed him up a couple hours ago, and then left to run an errand. So we have a Fighter with Wizard buffs on (Energy Resistance, Spell Immunity, etc.) and again, it's not like the DM has to explain every defense an NPC has against the players.
KarinsDad said:
If Orb spells are not broken, why would the DM have to craft BBEGs with specific defenses against it?
He certainly doesn't have to do that, but the option is always open to him. Have you never had a BBEG that had Improved Evasion? That pretty much cancels out all AE spells. So it's not like you are specifically designed him to avoid the PC Wizard's Fireball spell which he uses all the time. That's just a particular defense he has. Against Scorching Ray, he's not so defensive. Same with the Orbs. A particular BBEG might have a particular defense agains that, but not against AE spells. Again, it's not like the DM has to explain an NPC's defenses to the PCs before, during or after the encounter...
KarinsDad said:
Nobody talks about crafting BBEGs with specific defenses against Fireball because Fireball already has at least one defense that all NPCs already have (i.e. a saving throw). The BBEG does not need a specific defense against Fireball. General defenses (e.g. high hit points and a decent Reflex save) might suffice (situation depending).
There are several spells which deal damage or harm an opponent in other ways which bypass saving throws. Why are Orbs so special in this regard?
KarinsDad said:
But Orbs have so few significant defenses that the DM would have to purposely alter his BBEG and/or scenario, just to take them into account. He doesn't have to do that for Fireball.
Isn't that the DM's job though? To make challenging encounters? To think of ways around the PC's offense and defense? Sometimes the PCs will wipe the floor with NPCs, other times it will be a close call.
If you are running an encounter straight from a module, those encounters do not take into account all the variant books and such that are out, so often times the DM will have to improvise if he wants that encounter to be more challenging. If the DM makes up his own encounters, he is already altering the way the NPCs will react to the PCs to begin with, so he just has to take certain things into account. Whether it is Orb spells, Wraithstrike, or what have you. That's part of being a DM.