Two walls

Characters that have two walls have one defence that seems pointless. Squire training dummy and AL colossus.

Why aren't there more useful defences in their places?

Colossus should be good at the du cost but I've used same empty relic for it and skeleton Orc and the Orc lived longest.

This could be to do with luck or size and I accept that.

Someone tell me how to use squires dummy and colossus in an effective way.

The dummy is meant to be a hybrid of a dps tower combined with a wall. It just isn't quite good enough to be used often. You have a good point in that if the dummy wall was made stronger, there would be no need to use the spike wall. With the new onslaught mode, we may see lanes that the dummy is more effective on. There is also a dummy shard that transports enemies back to the lane spawn. That hasn't been useful because most people can build in a way that mobs don't typically reach the walls. Could be useful in the higher floors now though (like the lanes where enemies are weak out of the spawn but grow stronger as they travel down the lane).

The colossus is also a hybrid tower, but it is a little more useful. Just like the volcano and the obelisk.

The dummy can actually be quite useful when dealing with 200+ enemy lanes, the colossus is the reincarnation of a 1-man army and the strongest wall in the game as of now. If it goes down before your other blockades its (probably) your fault because you didn't build out the lane enough.

Is there any specific shard build to make them really good.

I considered fortification, vampiric empowerment and press your luck for the dummy but I can't tell if press your luck breaks the crit chance cap.

the other thing about the dummy tower is that most of the time when your walls do get hit  it's a ranged attack. The dummy doesn't hit ranged. If the dummy reflected projectiles bases with damage based on how fast it was spinning, then it might be more useful and we would have another reflect defense.

@tehgak quote:

the other thing about the dummy tower is that most of the time when your walls do get hit  it's a ranged attack. The dummy doesn't hit ranged. If the dummy reflected projectiles bases with damage based on how fast it was spinning, then it might be more useful and we would have another reflect defense.

Now I want a shard for that.