Generally, the cross realm BG's worked out and I'm a fan of the much reduced waiting times for an AV run. Even with the anti-AFK measures it still only takes a few minutes as opposed to the upwards of an hour it could take before. But I do see some logistical problems in setting up a similar system for instance runs: no more summoning stones since everyone is on a different server, for example. Everyone would have to make their way to the dungeon themselves like they used to in the dim, barbaric past when cavemen first played WoW.
What do you think? Would we need 'Instance Groups' similar to Battlegroups, or would you just extend the Battlegroup to also be the pool your cross-realm LFG pulled from? Is this even an issue or are folks overestimating how much faster level will effect instancing?