I've gotten every single garanteed champ I've gone for.  You stated your own problem in your first sentence.  If you are garanteed a champ on the 30th shard, and you don't have 30 shards, and you open less than 30 shard, expecting to be garanteed the champ, then there is something wrong.  And it's not the game that is wrong!

Sorry to hear about all your other complaints.  If you're not having fun then you should find something better to spend your time on.

I think if you focus on getting your champions to 60 through brutal 12-3 - which will then help you farm dungeons a lot more efficiently - you'll find you're able to acquire resources a lot easier in the game through Clan Boss, (eventually) Doom Tower, Faction Wars, etc. It seems like you have some misconceptions on how to approach the game, and I think if you take a look at the videos posted in this thread: https://plarium.com/forum/en/raid-shadow-legends/674_game-discussion/613769_celestial-griffin/

You'll have a much more enjoyable time in the game long term. Getting those champs to 60, being able to equip them with banners will make your life a lot easier, especially as it pertains to getting speed up on champs. 

As for guaranteed champions: events like these - much like fusions (which will I think will end up being a better use of resources for you) - require planning and saving for most players. If you're not doing fusions, saving your shards for 2x's is going to be the way to go. 

Here are those videos for you, A10C:

Here's a video on the basics of farming, produced a long time ago by Raid:

https://youtu.be/Ho3yE7kSN6A

Here is a Hellhades video on farming that goes through basics. I think this one will be a big help and goes step by step through the beginnings of champ farming to more advanced efficient dungeon food farming:

https://youtu.be/mzSCEGQJ3dI