I’ve had a go with a few types of LatD armies. Last year I used this:
1) Coven + Land Transports + Hydra
2) Coven + Land Transports
3) Coven + Land Transports
4) Coven + Land Transports
5) Coven + 2x Cultists + Land Transports + 2x Hounds
6) Coven + Land Transports + Hydra + 3x Hounds
7) Coven + Hydra

Coven + Hydra
9) Doomwings
10) Doomwings
11) Doomwings
12) Firelord
13) Firelord
155 units of LatD fun. It did alright until I faced TRC’s scratch built orks and totally failed to do anything against a big gun mob.
This year I experimented with this:
1) Coven + Land Transports + Hydra + Daemon Pack
2) Coven + Land Transports + Daemon Pack
3) Coven + Land Transports + Daemon Pack
4) Coven + 2x Cultists + Hydra + Daemon Pack
5) Plague Zombies
6) Thunderbolts
7) Defilers

Slaanesh Daemon Knights
9) Slaanesh Subjagators x2
Daemons – 1 Greater Daemon & 12 Lesser Daemons
98-113 units. List did ok until it self destructed against a Warlock titan.
I must admit that my experiences have lead me to believe that if you are going to use lots of daemons then you need Icon Bearers, but with all the other benefits the character has they are too expensive. I would also like to see a dropping of daemon stats and resulting price decrease.
To be honest in the future I’ll probably be leaving the daemons at home as well as the upgrades to the covens and trying to fit as many support choices as I can into the army.
One thing that I’ll say though is don’t be afraid to have factions that hate each other as a 6x4 table still gives you plenty of space to keep them apart.