Check out this handy link (https://i.imgur.com/yfAy17z.jpeg) when you have a moment to look at the drop rates for the various CB chests.  As long as you meet the damage requirements for the chest, you will have a chance to get the contents available for that.

For example, the Grandmaster chest for Brutal has an 11% chance of a shard, and 2% chance of a book, so you really need to be getting them consistently over time to get any sort of return.  The chance of a skill book jumps up to 15% for the Ultimate chest on Nightmare, but that is still a 85% chance of not getting a skill book.

Some days you will be lucky, some days you won't.  

I mentioned every day dmg over 70 million at nm for almost 2 months and no shard, and someone else in the clan with dmag smaller than me receives a sacred shard how the hell can it be explained 

CB drop rates are not determind by someone doing more damage than others.  It's simply doing enough damage to reach that chest bracket.  

For example, the Ultimate chest on NM needs 39166k damage, which is about 39 million.  Once you get over 39 million damage then you are eligable for that chest, with the percentage drop rates that it comes with.  Getting 100 million at that point doesn't give you any better odds of getting good gear from the chest.  100 million and 40 million both result in the same chest with the same drop chances.

In other words, don't aim to be the highest damage dealer in the clan.  If you can comfortablly get 40 million on NM with 1 or 2 keys, then you are better off using your other keys to hit Brutal, and then Hard, to get more chests.  

Please watch your language OP.

there is no confirmation that placing first in damage nets better rewards but I like to believ eit is the case, even so the rewards are pure RNG. 

I apologize if the curse is interpreted in translation, I use google translate from Romanian into English and grammatical mistakes can creep in. 

There iss no way you got 0 shards/books in 2 months from top chest on NM.  You likely had a bad week of rng, we all do.  It balances out.  UNM is way better, but even NM is really good sometimes.  Yesterday I got crap from UNM, but 2 sacreds AND a lego book from NM.  Today nothing of note from either, but a blue shard from Brutal.  Just rng...

I got a sacred shard from NM CB today actually

Its not  important to be doing the most damage in the clan because I have got sacred shards before from NM CB and was 2nd highest damage

The only important part is that you are doing enough 'total' damage to recieve the last chest