Bloodthirster is always a popular choice by me...I love mine. Unholy might is a must have as well to help with anti-tanking. Blessing of the Blood God is only 5 points but its rarely used (at least in all the fights ive had) I've never ever had a need to use it.
Skulltaker again a good choice especially putting him in with a group of bloodletters. helps with his survivability.
Bloodletters, for a start drop the instrument. You should never ever end up drawing in combat with letters. So the points invested in that to me are a waste. secondly id consider dropping their number down to 15. Only reason why i say this is because if you deep strike them in, a group of 20 PLUS skulltaker is going to take up a HUGE area and you will most likely end up on the mishap table. You don't want that when you have invested so many points into one unit.
daemonettes....i've never had a good experience with my daemonettes. Despite all their attacks and high initiative, because of their low weapon skill and strength they rarely get any attacks through to anyone. If you want the nettes go for it but I'd suggest losing the group of 9 (only go for a minimum of 10, survivability is what counts) and instead with the 5 letters you took from the other group make another group of bloodletters (they are much better i have learned).
As everyone else will no doubt say only bring grinders in groups of two. While this is on the whole true I have found a great tactic for keeping one single one alive. And that is engaging it in combat with the biggest unit of troops you can find ASAP. Most of the time the dont even have a power weapon, they can't hurt you and you have taken out a HUGE proportion of firepower out of the game. That does mean however that phlegm and tongue are pointless so you can save yourself some points there. But it is better to just take two grinders or none.
The prince (i love my princes) i would drop Noxious touch, most units he will be wounding on a 2+ anyway so no need for that (i never put it in) and i'd lose aura of decay and replace it with daemonic gaze or breath of chaos (much more effective).
If it were me I would try and get more shooting in there and where are your elites?
Dropping the blessing on the thirster, 5 letters + instrument, 9 nettes, soul grinder, and prince upgrades will give you 421 points to play with. That is plenty of points to buy some shooty with.