Hows thie for a 6 tie crack squad:

Howl w crack

Zeta leader w crack

4x blackcracks

Cowboy Kenny ran this at the Plano regionals. He just missed the cut at 20th place, so I think he did quite well. Zeta dropping a random 4 dice attack on you super hurts.

That's exactly what Dallas used to win Fresno Regional.

It's so easy to overlook the value of these guys until a skilled young pilot show you how...

In my lists I try to make if I only have 3 ships I try to trim 12 points down so I can take one of these.

I still think for beginning list building the 4 ship (large ships counting as two) is a best way to set up keeping a mix of Aces and blockers.

TO answer the OP, we don't see it not because it's bad - quite the opposite, in the current meta crack swarm variants are very good if played well, as evidenced by one winning Yavin - it's because a: they take a lot of practice and a lot of brain power to fly, so across a 6-game tournament they lead to more player fatigue and mistakes, and b: they take a lot of time to fly well, so in a timed format they can actually be a liability if you don't manage to get the initial engagement right against aces, because they can pick off one or two TIEs and then dodge forever for a win on points, especially if they control the asteroids well.

Swarms, particularly TIE swarms, are one of the major counters to jumpmasters, but they're a LOT harder to fly and a lot harder to *learn* to fly than jumpmasters, so we don't see them as much.