On the contrary smaller squads tend to get wiped by grenades more often than larger squads. Can't remember the last time I had a conscript squad deleted outright by a grenade where as it happens quite frequently with Grenadiers.
An instance that would have wiped your squad would have been avoided so this buffs smaller squads more than it would with larger squads.
Also to clarify a 2-3 model cap doesn't mean the rest take no damage, it just means squad members killed would be capped.
Imo the only annoying about the rifle nade is how powerfull it is vs units clumped in yellow cover.
Units tend to clump up in yellow cover. Allowinf for easy wipes from long range.
I would nerf its damage in yellow cover a bit.
The rest is fine, this way you will still do very good damage vs clumped units in yellow cover without outright wiping full health squads (wich is the only problem) You will also be able to destroy the yellow cover and have improved accuracy on the inf.