Plenty of solutions.
Some hard counters include:
MGs to suppress
rocket artillery to saturate an area
commander artillery abilities
WP smoke (allies)
tanks & infantry
"Passive" counters include:
planting minefields
planting demo charges (allies)
baiting the blobs into supported areas (demos, mgs, etc)
using smoke to break LOS
mortars to provide support
planting flare traps (USSR) for early warning and provide los for mg's
or, you can squish them with tanks
The best way to counter blobs is to use combined arms and outmaneuvering them. Don't try to outblob them.