If Middlesex were to be docked some points for this then they, and other counties, would need to think very hard before using outgrounds in future.Warwickshire already 2 down v Essex (1 of the lbw decisions very iffy).
With the best will in the world the drainage on outgrounds is almost sure to be inferior to a County ground.
Been a few years now but I remember super soppers being sent over from Leeds to help dry up Scarborough to get a game on.
I'm sure Middlesex did something similar, heat lamps have been mentioned.
If the Umpires report that the ground staff did everything reasonably possible to get play on then that's the end of the matter, and rightly so.