i remember the only 2times i started Total war Multiplayer
#1 Rome Total War: i spent 5-10min customizing a well rounded army with archers, inf, cav, arty, support etc.
my opponent had a full stack of cataphracts only (only and full stack) and double right clicked me to death
#2 empire total war: i took austria, used inf cav support etc. again. same thing, but this time with English red coats. got right clicked to death
Blobbing =/= Spamming
I'm talking about archer units being blocked by units in front of them, napoleonic rifle infantry having to fire by rows or they will be blocked by the units in front of them, shogun 2 gunpowder units which need clear line of sight to fire on the enemy.
Blobbing = You concentrate all the strength of a group of units (usually in a huge group, hence the term "blobbing") on an enemy unit to destroy it before it's able to retaliate in any way, thereby basically winning an engagement for free.
Spamming = Using a large amount of a certain unit because the enemy has failed to field enough counters against said unit to render those units useless. Doesn't necessarily mean they are all in the same spot, unlike blobbing.
Blobbing can counter units designed to counter them by simple force of numbers. Spamming is not the same as blobbing.
Also, I've played total war games (the ones put out before the franchise was turned to utter shite by CA), and cavalry units are just very strong in general. However, using them in a mass blob is not effective. I highly doubt your opponent was "blobbing" them. They might have been using a lot of them (spamming), but putting them all in one big square and running at you would make the cataphracts much less effective.
On a side note, TBQH Total War's multiplayer system is just retarded in general because you've no idea what your enemy's army composition is beforehand. If you had known beforehand that they would be fielding straight cavalry, and they were "blobbing" them, you could have easily countered it, unlike in CoH2 where if you know your enemy is blobbing and you build counters, they can just instakill them before they even get a chance to do anything.