The main problem here is that they made swb cross server in a very * way.
Right now what happens when you click on register is what follows:
You are immediately teleported to one single server together with everyone else in your spacetime bracket clicked on register (that explains why your world chat have people that aren't in your server and that aren't neither in your field and why you can't anymore chat in group, because in the 'new' server there's no group). At that point it begins a sage world battlefield with all the people that went in the unified server. The point is how the people are distributed in this case.
If in one single server there are more than 75 people (and this is the case of the unified server we are all projected in) is not true at all that the top 75 go in one battlefield and than the following 75 go in the second battlefield and so on. What happens is that the top 75 get split in 3 and are projected in 3 different fields. Field 1 have 1-25, field 2 have 26-50, field 3 have 51-75. At the point the people in 76-150 range are split too and 76-100 go in field 1, 101-125 go in field 2 and 126-150 go in field 3. The same happens for 151-225th, that go split in the same way. Only since the 226th you get selected for a full new sage and people in 226-450th place are split in the same way. This explain why there is a so wide difference in the top3 battlefields ane why the difference is a lot lower for people around 300-500th place in your spacetime bracket.