Let me help you out: a gem sink is an event that costs more gems to participate in than you get back and that continues to require gems for additional participation.
Guild Wars requires a single up-front gem investment. The reward for winning the event is considerably more gems than you put in. Not a gem sink.
Every other event, every single one, fails to give back the gems required to participate in it at a high level and requires continued, infinite incremental gems to continue to play. They are pay-to-win in the purest sense. They are gem sinks.
The only way to come out ahead in gems in these P2W events is to not spend any gems on them and take the small rewards given for minimal participation. What we are wanting is more events that give one a chance to emerge with substantially more gems than we started with if you place high in the event.
In other words, we are asking for fewer gem sinks.