Agreed. They come way too quickly for how much damage they do. On the other hand, I would mind my enemies surviving a catapult strike on the head...
So this is what they should to for all AOE feats coming from above:
1. Time between calling and incoming should be increased to at least 5 seconds
2. No outline on the ground for the enemy for where it will hit
3. Audio cue for both teams so that they know something is coming
This way, while they will still be as deadly, they won't be as save, because it takes 5 seconds for them to land. At the same time they will not be useless, because the enemy doesn't know WHERE they land. So a bit of planing and strategical thinking will be required to use them effectively.