Well I have written up the
latest test, and the results were - interesting.
DaemonsThe 'big' chosen, + GD, + DP and no less than '4' LD advanced through a storm of OW fire - and then the GD died to my usual luck

. Even so, the remainder of the formation had enough normal and MW dice to wipe out the remainder of the IG HQ. But it did raise a couple of questions:-
1) Do the formations that lose units "sucked into the void" get BMs as a result - we presumed so, but it is not totally clear.
2a) A carefull reading of Daemons and summoning suggests that the daemon pool contains 'factionless' daemons. It is only when the daemons are summoned to a formation that they turn into the relevant type for that formation - is this correct? We played 'Khorne' Chosen and 'Tzeench' Retinue and Forlorn Hope, so if correct it seems that the greater Daemon could have become either. However, this seems to make daemons even more powerfull as you can tailor them to suit the intended strategy for any given formation. If this is true, they are definitely too cheap.
2b) This also suggests that a damaged Korne GD could return as a damaged Tzeench or Slaneesh GD - which does seem a little odd.
3) Given the power of the LD, I do wonder if the GD is actually worth it on the current costings. Especially as, if you only throw a total of '6' (and assuming you have sufficient LDs) 6x Khorne LDs give you 12 assault dice, while the GD only gets 6x dice (albeit with instant kills if the TK attacks strike home).
4) Is there anything stopping people from adding the upgrades to a single "uber" unit? I would presume that the DP cannot be granted the other characteristics as he
replaces the unit, but just want to check.
5) If you have an Icon bearer in a formation, is retaining daemons mandatory, or can you opt to send some back to the pool? This is not entirely clear, so we presumed not.
6) In the game, I had 75 points spare at the end which were spent on the second obliterator. In hindsight, I  think three more daemons might have been better - 7 LD was not really sufficient for four formations.
7) Final thought - we missed the point that when Chosen#1 broke, the remaining two daemons should have vanished.