Personally I have stopped mine at L23, due to the exhorbitant cost to take them to L29 (and also comparatively smaller benefit).
A fast hero already charges at 8 tiles. Getting the Average to 9 tiles means that (more often than not) the Average & Fast heroes in my team charge at the same time.
My war teams I also tend to build around two premises:
- Having a cleanser on each team
- Having heroes who are all mana charging at same/ similar times… So for me, dropping a Fast down to 7 tiles doesn’t really yield much benefit if the supportnig heroes for that sniper are not yet ready (e.g. Lepus charging in 7 doesn’t have much benefit if I have to wait for King Arthur to charge at 9 anyways).
My personal strategy has been:
- Mana to L17
- Crit to L10
- Mana #2 to L11
- Mana #1 to L23
- Mana #3 to L11
After that I plan to:
- Ninja to L10
- Mana #2 to L23
- Mana #3 to L17 (slow break)
- Mana #1 to L29 (maybe)
Regarding troops for defence, I also think that the difference between a L23 and L30 mana troop is fairly minor in the end. I don’t have any L30 troops but my defence team is one of the top 5 performers. The heroes make more of an impact than the troops do.