Pre-emptively, I seem to recall one of the blast shapes (eldritch doom?) functions as an area of effect that does not require an attack roll. I can see the argument for allowing a warlock to cast with these modes on since most of their eldritch blasts use touch attacks unlike a fireball, but isn't this just encouraging every warlock to run blast shapes with no attack roll full time in exchange for +10 AC?Eldritch Armor: No longer grants 5% physical DI. Instead, this feat now lets warlocks cast Eldritch Blasts without deactivating Expertise or Improved Expertise. The usual -5/-10 AB penalty will apply to the touch attack roll.
Tangentially, has any consideration been given to allowing other casters to stay in Expertise/Improved Expertise if the spell they're casting has an attack roll? Say, for example, inflict wounds, or a healing spell on an undead, which require both attack rolls AND saving throws?
Edit: Perhaps, if this is a perk desired only for warlock casters, it shouldn't work with blast shapes that don't require an attack roll?