I don't know how true it is, but I heard that in the past William Paterson sent out acceptances in waves. I received my acceptance about 2 weeks ago and a deposit is due on April 15, if they are doing waves I would assume that the next round of waves would hear after April 15. I cant say anything for Seton Hall as I did not apply, but I heard back from Kean well over a month ago and deposits were due before I even heard back from any of my other schools.
Give Kean admissions a call and ask for Brenda - she has been EXTREMELY helpful to me throughout this process and I assume she can tell you if there are still some decisions that have not been sent. Also, the address they sent my response to was slightly different then what I put on my application - if they made this mistake to others it is possible some letters have not been delivered.
Good luck!