Let me give you an example. What I do with my assault volk spam is target a group of infantry (who tend to be in groups of 2) essentially suiciding that unit to distract the other commander. The other commander now has a choice; he either micros that squad or he defends against my flanking puma/P4/ostwind/etc. If he choses the former I win, if he chooses the latter I win.
1) Send targeted squad away/into building/into transport/behind armor.
2) Deal with other shit.
Really isn't that hard. It can be kinda annoying but that's about it. I've dealt with Volks spam before (both Defensive and Blitzkrieg), and it really is nothing impressive.
The defensive buffs are there because once you lose control of the squad they will willingly leave cover, charge through a minefield, past an MG and into the barrel of a Sherman. As I said before, the defensive buffs are a bit over-the-top, but I cannot see it being justifiably nerfed past .75/.75.