It's way to easy to counter this. One or two Magikill using poison and/or explosions would destroy large portions of the Swordwrath within seconds, with this made even easier with prior defences such as walls and castle archers.
Generally, in the late-game (and to an extent, the middle-game) Swordwrath are quickly obsoleted due to their low health and melee range. As such, large numbers of Swordwrath are usually a waste due to the fact that one could quickly lose them. On a similar note, massing large numbers of a single unit is rarely a good idea. It takes too long to build and resupply. As well, the lack of diversity in units leaves you with fairly limited options and situations that favour you.
Funny thing is, T1 units have their uses in early game and late game, but suck at mid-game. Swordmass will kill Chaos giant mass (I'm serious), Crawler mass with support and a giant is effective late game.
