Cost/Benefit Analysis of Rushing to Thronebreaker
After seeing the latest calendar, I think there is a pretty strong argument now that anyone that can rank up a R3, should probably rush to do so. Even if it's a lousy champion you will never use. You just have to bite the bullet and treat it as an investment to get into the club.
Yes, it absolutely sucks to waste a T5CC like that, but the benefits are starting to add up quickly. First, consider this-- Every month you are TB, you get access to:
4x5% T5CC from glory
1x5% T5CC from calendar
0-2x 5% T5CC from daily crystal (depending on your luck, maybe more)
So we're talking 25-35% of a T5CC every month, as a baseline T5CC gain just for being TB.
Now consider this-- How many months do you think it will take for you to pull the god-tier 6* you want that also matches your T5CC?
If your answer is more than 4 months, you're already in the negative T5CC-wise. You might not have spent the one in your inventory, but you still lost one regardless.
And this is just the baseline. We haven't even talked about the progression based-rewards like the two calendars and two gifts from this month. Nor have we considered the other 27+ days of daily crystals and monthly calendar rewards.
So with all this in mind, I think if you're cavalier and don't have a steady source of T5CC (e.g. AQ7), you should strongly consider completing abyss and treating the T5CC you get as a ticket to become TB. You'll make it back in 4 months at most (probably sooner).