Pax. They have jump shoot jump. They will always be in cover, or behind los blocking terrain.
And, they will be engaging you at log range, where you can't just rapid fire them down.
Then, when you get close, they will redeploy 48 inches away.
For the points of a tactical squad, you get more shots, more strength, more mobility, more survivability, no need for a transport, and still obsec.
How many armies can spam AV 13/14?
Necrons (but that is not the good build) imperial knights (if you can call that spam)...?
How can you not see that this unit is a game breaker?