I honestly think the solution to high-build-cost takeouts being negated by a level 2 spell was implemented the moment that Prepare to Die went away. As someone who plays a Scout, I can assure you that I have never had a Terminate blocked by a Magic Armor, because the time to cast a magic armor after my first normal weapon blow (which pops the dumb defense) is longer than the time it takes me to deliver a Terminate. No warning means that a dumb defense like Weapon Shield simply can't block an intelligently used powerful blow.
I also think the effect group-based Spell Shield does more harm than good. The original post reasoned that PCs are frustrated by wasted abilities. Changing Spell Shield doesn't really help this concern much. NPCs generally use protective spells much less than PCs (most have built in smart / dumb defenses and aren't spell casters). So, at least in my experience, this change hurts PCs much more than NPCs. Furthermore, by making a protective effect group specific, now the only way to break the protective is with a spell of the same effect group. That means, for example, it always takes two Prisons to land a Prison spell, because no there is no other attack spell in that effect group. Similarly, if you are trying to land a Sleep spell, you can only break a Spell Shield with a Shun or an Awaken (or a Dominate, but that is higher level). In short, PCs get the shaft again because they no longer have the ability to throw a 1st level spell to break a Spell Shield and then hit with something impressive. Thus, this results in PCs burning even more powerful resources than before to break a Spell Shield when it matches their take-out spell (or just being incapable of breaking a Spell Shield). Finally, it must be remembered that all effect groups can possibly be linked to all delivery methods. A Spell Nausea (Alteration) is rare, but not against the rules.
Note: <X> Shield does currently exist as a monster-only ability in the current rules set, though it only cares about effect group, not about delivery.
-MS