If you aim them right, infiltration grenade will destroy any house. Basically try to aim at the center. The spread of the thrown grenades will do the rest and damage all 4 outter walls enough for the building to collapse. That being said, DONT change it.
OKW is fucked vs garrisons anyways and you are forced to choose a specific doctrine for these grenades, already narrowing down your choices for the late game...
Little fun fact: Because of this very very cheap abilities opportunity cost, Ive often found myself throwing these nades at everything that moves, thus postponing shrecks by quite alot of time, making me open and vulnerable to a tank rush. Isnt that what every allied fanboy always wanted anyways? ^^
Nerf Infiltration Grenades, buff ISG, everything gets what it deserves.
I would also take issue claiming tossing Infiltration Grenades very meaningfully decreases Schreck buying, because those things are ridiculously cheap and a good opportunity for them is the same as a good opportunity for a regular Model 24 at a
third of the price. My use of the ability has never made me think "My Volks might be regularly shredding their infantry with grenades...but when they do that nine times, they'll have one less Schreck!
", it's that cheap.
Now tossing three Model 24s, that's a noticeable and fair trade-off against a Schreck with 6 less squad-wipes for enemies to dodge. Plus the cooldown of it actually does stop Volks from spamming the things every time they fight so it's hard to suck away all your munitions on Infiltration Grenades even if you wanted to.