I've just stated how it felt in Arena, for me personally and for my arena partner (Enhance Shaman) was worse now then before. Comparing 10k + 1.5k Queue and 11k + 600 Queue. It wasn't great at 10k either, but it was slightly better then last night. We'd all love it to be 15k online and that it works like 1ms for everyone, but in reality, this can be avoided maybe. We just have to try and be online before peak times and play then.
No one is blaming you for that, it is how it is, once again personally it sucks for me because I'm Feral (Melee), didn't see any Healers or Ranged classes complain, because they do not encounter the "Out of Range" problem even when you're on top of a player. So easy "fix" for us is to try and play before peak times or after it. Until the core is implemented to other servers and population goes down a bit.
So at the end of the day, you did right by increasing Cap, it helped 1000 people to play, but it also hurt a bit the Pvp scene, but there is a workaround for that for most of the people, not everyone will be able to avoid peak times in order to do it, but... it can't be helped at this moment.