I think what he is saying is that ambushes are nasty to pretty much everyone equally. If you get ambushed, you are screwed and it doesn't much matter who you are.
And crafters are the best suited to defend against ambushes so, in my personal experience, ambushing a crafter is completely futile.
Regarding your example, a wizard who is spending rounds putting up blocks and extending them is not attacking, which makes them less deadly despite being temporarily invincible.
I'd just ignore the wizard for 8 rounds and focus on his buddies. Or do maneuvers for 8 exchanges, then, on the 8th tag all the maneuvers. And to make the example fair, let's give the opponent equal refresh to the wizard. Athletics 4, supernatural speed, mundane armour etc... Toughness and recovery. The wizard isn't nearly as useful anymore attacking with that sword. Hell, or just have the guy go full defense until the duration of the spell runs out.
The guy is dodging at +8.
Now, ambush both these characters. They are both dodging at +0. The wizard probably has a block item and the other guy has toughness. The crafter laughs and laughs and laughs.
Edit: I'm taking this post from another thread to accentuate a point:
Yeah, I had a game once where the party bruiser was rolling from 14 with alarming regularity.
That group really took to the whole teamwork and maneuvering thing. It was pretty spectacular.
So, by round 3 the bruiser hits the wizard with a +13 attack (by attacking at +7 and tagging 3 aspects), and obliterates the wizard's shield. Now the wizard has no shield and has used up his 3rd and 4th mental box, taken backlash and has yet to do anything useful in the fight (except, maybe soak up some action from his opposition).