@Marathon, I'm on NA, and we actually play together quite often, though my character names are different than my forum names.
Currently my most active characters are a cavalry HA hybrid, and a polearm wielder. With 6, soon to be 7 PD, one-shotting a full health cavalry is rare. On my HA, who currently is only using a rouncey, only the occasional super high PD/Longbow archer can take out my horse with 2 shots. Additionally, I have to be closing in on the archer for this to happen.
As chestaclese has pointed out, balancing a game where one character requires multiple characters to be defeated hints at an imbalanced game. Additionally, the situation you described of the piker/archer combo is pretty romanticized, and as someone who has played with you as a horseman, it is very rare.
Occasionally you will see an organized squad, but most of the time, if I'm focusing (which often im not!), I can swoop in and get a guaranteed couple of kills.
Another factor you are leaving out: organized horsemen. In the situation you described, a lone horseman can be killed by a greater number of players. However, on a level field, if you have the same number of infantry versus an equal number of horsemen, if both teams are equally organized or disorganized, the horsemen should come out on top in the current patch.
Archers? Guess what, horsemen are also very deadly archers.
Throwers? Thanks to the patch, the top tier throwing weapons are inferior to low tier ones due to ammo restraints and nerfs. Throwing is now a minor annoyance.
Pikes? Still a problem, but much less so of one thanks to the fact that very few people on the battlefield use them. They are a highly inconvenient weapon.
Xbows can be pretty damning, but they need cover to be a threat.
And remember, player skill always plays a strong part in this. A single ancedote or example most likely won't carry a lot of weight. Keep your eyes open, because you're going to see more and more cavalry and HA this patch once people start catching on. You're also going to see these players do better than they normally do with an infantry character.