You have a 1.4% chance of getting a rare champ from a mystery shard. The odds of pulling 300 and not getting any are, ironically, 1.45%. Put another way - roughly one in every 650 people who pull 300 mystery shards will get no rare champs from them. Guess you're that person.

That said - that specific advanced quest is absolutely a trap. Don't take it again.

I  wouldn't  take  that  quest  UNLESS  i  knew  i  were  about  to  open  2k  plus  for  an  upcoming  summon  or  training  event  event.    I've  never  actually  taken  it  but  I  could  see  it.

It's exactly as kram said, just not a quest we really ever want to take, unless you're doing precisely what angwil is saying which is 100% going in with the knowledge you are opening a stack of mysteries. Even then I just can't imagine taking it unless I was desperate. Would rather just take a doable Expert quest, if possible. 

I will open 2,000 mystery shards next week for the summon.   This clan quest seems a lock for me.  

I wish you the best of luck. :D

I hope you are Irish because I need all the help I can get.    lol

It certainly feels that way, Plarium will no doubt deny it (like they deny stealth nerfing sacreds and leggo books from transcendant chests) 

The thing that gets me is that why do we have to fight our own clanmates for the decent quests? This was very short sighted considering there are legendary champs in the offing, it is splitting clans up.