Looks good so far. You could consider adding gutrot spume for deep strike shenanigans. I would opt for perhaps 30 plagueboys for getting bodies on the board or some other hoard unit (maruarders or plague monks) but they kinda loose their edge without the glotkin.
I really enjoy having a GUO allongside my Blight kings for the extra movement, it can be very valuable during the game.
And no deamons are not needed for contagion points, these are due to the alliance towards Papa nurgle. But you might want to get some for summons.
So to be fair you have 2 routes; all out mortals with maxed out blight kings 35 Ish or more bodies..