Agreed that they can't win the game all by themselves. Pikes also have to work in conjunction with flanking units in order to be most effective... just as they were in real life. A square of 36 pikes (6x6) is quite "horde" enough, provided a unit of duelists (with pistols) sits on each of its corners.
Yep. Fast Cavalry with spears provide a capable 'flank guard' as well, courter-charging pike-chargers and gaining you time to engage with your phalanx.
Its worth noting that in 8th edition it seems you must posses two full ranks of your own to break enemy ranks, and thus the tactic of hitting a unit in the side with a half doze fast cavalry while engaging them in the front will be much less succesfull.