Ninja event start times are inherently unfair, depending on your international time zone.
The event may start in your time zone while you are at work or are asleep, leaving your base free to attack. Trophies become hard to retain. On the other hand, in another person’s time zone, the event may start conveniently in the evening, giving you plenty of time to gain and retain trophies.
For instance, if you are based in Europe (CEST), the start time would be 5pm local time. If you work full time, or are at school, there’s no sensible way to retain trophies over the course of the day, simply because you cannot log in. The situation is even worse if you are in new Zealand (GMT+12), since the start time would be 3am. On the other hand, for instance, if you’re based in China (GMT +8), the start time would be 11pm. This gives you plenty of time after work or school to gain trophies by playing, and/or retain trophies by staying logged in.
At higher levels (5300+), it’s almost impossible to retain trophies by defense alone; you must keep raiding to gain trophies. I am not aware of a base that is impossible to defeat. So it is clear that, in order to stay in the top tier (5300+) you must play for an hour or two before the ninja start time. However, as noted above, this is almost impossible if you are at work or school.
I’m not saying you can make this fair for everyone (e.g. if you work night shifts, or are going to go out with friends on Friday evening).
However, my point is that for many with 9am-5pm lifestyles, depending on your time zone, it is almost impossible to stay in the top tier. The ninja start times can strongly bias whether you play in the top tier or not.
Since many alliances are united by language, and hence by country and time zone, this in turn favours certain alliances, and disadvantages others.
Please, please, please investigate this. There must be a fairer way to allocate tiers that is not dependent on where you live in the world.