I'm not sure exactly what this argument is about anymore...
Anyway, I have seen blocks be useful. If you're clever and willing to wait for the right opportunity, you can do a lot with a block.
But in your average fight, blasting is better. And the Harry Dresden-style short-duration one-person shield is almost never a good idea. Good blocks tend to be proactive, long-lasting, and group-friendly.
Totally true after the first attack...but unless they have a lot of Lore (or something else appropriate), a 4 shift Block and a 10 shift block look about the same. Add in the whole 'Wizards are really dangerous' factor noted above, and not at least probing their defenses is not the brightest move. Or serious metagaming.
Actually, I think you ought to be able to tell the difference between a 4 shift block and a 10 shift block easily. Powerful magic generally looks about as powerful as it is.
And denying characters important knowledge that players have tends to cause headaches.
Dresden Files isn't a console RPG where every fight boils down to, "Hit the other guy before he hits you." Good enemies will have goals beyond simple annihilation of the other side, and a good GM will have enemies and scenarios set up so it's not simply a contest of who can make the bigger boom.
And, as stated, a good GM who remembers that DFRPG is as much a roleplaying game as it is a blasting game is going to play those enemies in character, rather than as super-optimized, hyper-competent badasses who can calculate battlefield probability on the fly and change their actions mid-course the instant it's less than optimal for them to keep going.
I really don't like this argument.
Maybe your enemies are mortals and you're worried about the First Law. Maybe they have hostages or bystanders.
A good GM will also make certain people react differently instead of just mechanically. In my games, if a man walks in when people try to gun him down, holds up his hand, and bullets do nothing, they are more willing to talk. That's exactly how it's worked a few times with Marcone.
Well, yeah, there's always Compels. But resorting to Aspect stuff generally isn't a good idea when discussing balance.