Not all Panic Demons. However, I know Prof A made an awesome defense (at least, I thought it was awesome...) with Wandering Spirit and the Panic Demons. With Tartarus and Gates for the recycle.
That is correct. I went 4-1 with one timeout win with that deck at the MN T2-Only last year. It was mostly successful because people didn't expect it. Nathan had an offense that was well suited against it though (Prophets + Hidden Treasures + Two Bears x3-5, with a bit of pre-block AoCP on the side) so that was my one loss.
However, I think I only had about 15 PD's, with 5x Wandering Spirit and 3x Fallen Angel. I would say that you can't build an effective T2 demon defense (PD's or otherwise) without including at least 3x Wandering Spirit (and you should use five). So if you did use 35 PD's, you would have at least 38-40 total EC's, which would make your defense at minimum around 50 cards.