Look away, look away.
The increased chance of being spotted when sneaking next to a monster now only applies if the monster is turned towards you (facing you directly or one rotation from that) at the end of your turn. So the chance of being spotted when sneaking behind a monster is the same as when not next to it.
If you are unsure of whether a space is behind a monster, check the percentage indicator before sneaking.
Generally monsters are facing whichever way they are looking. Let us know if any of the monster facings are particularly unclear.