We had a pretty good balance of targets for most of the upper guilds until recently... I'll let you figure out what changed that... but onto topic... I think that another solution would be to add in more claims or content. As far as content goes, upper thaz releasing as a T11-T12 would theoretically give 4 more claims and 8-9 more raid targets, which would work out ok. We had a big clog right at T10 a while back, and lower thaz really helped with the congestion. One of the reasons I think thaz is effective at releasing it is because each wing is a claim, allowing for plenty of content claims. Which leads into adding claims. I have heard that sanctum was split into inner and outer now, which is nice for that, Spires would be difficult to split... but Tur'ruj.. Perhaps try splitting it into separate claims by clusters of tribes, to help ease this sort of problem. I'm not an expert on Tur'ruj by any means, and can't really offer advice on where drawing claim lines in Tur'ruj would be best, but adding claims might be another solution beyond changing timers, or in addition to changing timers.
