First off it is a great target for such things as typhoon, devastators, land raiders, vendettas, and anything else that can sport a lascannon or deepstriking melta. So to field the Dais of Destruction is like playing a crapshoot on whether or not your opponent really has any high strength weapons. Melta guns really should not really ever be close enough to matter. Assault? nah, its armour 13 on all sides.
The problems are that it cannot move that fast to fire off its weapons. It also great slows down Asdrubael Vect and whatever you are teaming him up with. Both of which I do not like. Placing him with 9 other models also creates an issue on who you are placing him with. I mean do we really need 9 Incubi? If we place him with Warriors, then how do we get him into a unit so he doesnt get blasted off the board. Trueborn are another idea, so possibly setting them up as close combat units is the next big guess.
There are just so many problems with putting the Dais of Destruction into your list, that I have only tried it once, and it went down round 1 to a Vendetta. No it did not kill anything, it stunned the first and the second shot me down.
So the issue is not the vehicle itself, it is Vect. Having to place him inside with a squad of 9 models. Using the word Squad in the FAQ really bugs me. I prefer they use unit, as things like Squad can provide arguements. Vect really wants to be moving faster than this vehicle will allow. I will keep on trying the Dais, but getting Vect off and going is generally a priority. He is 240pts, and to have him sitting inside this vehicle really makes it hard as the vehicle itself wants to move slow and fire all it's guns.