I’ve only used them by accident before, never really found them useful though. The odds of a 3 star hero are quite good when you get them, but as discussed already, by the time you get to them you already have TC13 and there’s no point to not do that training instead.
I believe these TC levels should be changed to do something else. Some suggestions I’ve heard:
- Change them to get a 1*, 2* or 3* trainer hero of that color (or at least make it chance based)
- Change them to get a 1*, 2*, 3* or 4* star troop of that color
- Add 4* heroes (and maybe 5* heroes) of that element to them
Those are just some suggestions I’ve heard myself to make these training levels more useful.
Related: Training Camp - REDESIGN PLEASE
There is a master thread there with a list of different requests. Personally I think all levels are fine, except for 14 - 18 which I expressed my thoughts about them needing to be more useful.