I feel like you are probably a little light on Hag Queens and a Bloodwrack Medusa without shrine might be a tad squishy. The thing with Shadow Patrol is it eats up a lot of points, nearly 1100 in your list, which doesn't leave a lot of room for other troops. If you are set on using Shadow Patrol and Snakes I would probably cut one unit of Blood Sisters and the Sisters of Slaughter. I would use the points to add two units of Witch Aelves, an additional Hag Queen and either increase the size of your left over Blood Sisters to 15 or add another Hag and put your Medusa on a Bloodwrack Shrine. Both options would leave you with 30 pts for potential endless spells. Then again I am also new to the daughters, so take everything said with a grain of salt ?.
Also, if you are set more on Shadow Patrol than snakes @Aspirant Snaeper had an interesting concept for a Shadow Patrol list without snakes a few pages back. If you are ok with skipping the battalion, you could also look at one of @Scythian's snake only lists, cut a few snakes and add Doomfire Warlocks instead.