This is true for 1v1 only I think. Also, in 1v1 I am not having problems with blobbing for the exact reason you mentioned - I just go where the blob is not and gain territory. However, teamgames are more often than not very lane-y and that just leaves me with the blob head on. So yeah, Katy rush and a T70 seems to be it.
However, I do think it's not a very good concept that you can just blob in teamgames (very little micro, easy to execute) and your opponent (as ally) has to apply combined arms with a lot of micro.
Some 3v3+ map examples where this also works:
Essen - many side routes, angles due to the urban environment, especially on the left & rights areas where ppl are forced to split up for the fuel/VP/muni
Steppes - probably the most notorious map, being the biggest in the automatch maps if not game
La Gleize explains itself, esp with long retreat times and scattered points
City 17 I veto but it's got so many alternate paths that you can cap muni next to the enemy base without running into issues
Blobbing I dislike but it is what it is. It works for Axis players dealing with Allies too, if we don't want to blob. Sometimes I've felt like I'm being penalised for using combined arms to stop USF/UKF blobs. You have no infantry that can go toe-to-toe with an LMG blob until Obers arrive and maybe Pzgrens.
Katy is your go to yes, I'm just giving advice to increase pressure on them/decrease pressure on you before you get to T4. If your army's been battered and an Auf J's rolling at you, it won't matter how good your Katy skills are.