In my clan we have seen the same : Even 9.5' with some upgrades defenses see a well developped th11 as mirror ( yes I know need to look at the whole matchup).

The other issue is that it seems DARK is just to easy to farm OR hero upgrade times are too long. But seems that even for the moderately active player .. he / she can have heros uograding allmost 'non-stop' .. and with hero down a th10 in war is a HUGE liability.

On top of that .. players not in war for weeks in a row .. are also not the best attackers in war .. which makes them an even bigger liabilty.

Finally : th10 offensive upgardes ( cc, spell factory, army camps, labo and 1-3 key troops) are typically done in a month ... maxing defense takes a year. This means that in the 11 month period your th10 players are rated in war as ' max offense + average defense'. With the now increased weight on 'offensive' power this makes them an even bigger liability.

Time to move on to th11