I guess it's a toss up. If they follow the schedule they've been doing, I think next week would be a 2x Sacred Shard Pull. They would probably also have a champion chase tournament, which would net you  two books. No guarantee that's what they are doing, but just food for thought. If lego books are what you are after than I think your instincts are right.

The rewards for the summons are  nice (5star chickens and  legend  books). I am guilty of getting them all by pulling a few mystery shards just to get last reward

However ,what did I pull from all the shards?  6 sacred=epics  / 100+ ancients= many new epics and 1 dupe Legend

I managed to complete the fusion and got Iron Brago as consilation :D

I hope you will have better  luck with your Sacreds as I must be in mercy territory having pulled a few  other sacreds since christmas with no luck

Well I think Roxam is cool, but I'd suggest to just pull a few for the Iron Brago fragments (and maybe the first leggo book, that's what I did) Don't pull more than necessary though since we may be getting 2x sacreds next week. 

The void seems interesting to me, I ended up pulling her 

Nice pull!

0 for 1st 3 shards. Excruciat, bergoth, kytis 

Next 3

Torturehelm

Vogoth 

Rhazin (my first one is already booked, ugh)

I  only  pulled  two  epics,  Towering  Titan  and  Uugo,  but  Uugo  isnt  that  bad  so  Idk

Opened a bunch more to get books:

Armina

Warden

Alure (3rd one)

Knight errant

Bonekeeper

Vogoth (#2)

Old hermit jugg

Knight  Errant  was  my  first  epic,  pulled  him  when  i  was  F2P,  now  ive  spent  $20  plus  raid  pass.  Pulled  him  on  day  1  from  the  first  ancient  shard  you  get.