Personally, I think this is a good change, even if you can only join as a group and not a raid. Especially if you can only join as a group, actually. Joining as a group will let you reliably play with your friends(without the use of tricksy mods) but won't totally throw off Alterac Valley by flooding it with 40-man premades. You can queue for every other battleground as a raid, though, so Alterac Valley will likely be the same. I look forward to this hitting the live servers, I've missed the days of getting into the more 'epic' battleground with a group of my friends, even if we lost due to complete nubbery. Sure, you could still sort of do it with the aforementioned mods, but it wasn't very reliable and unless I'm mistaken, it was slightly against the TOS.
I'm unsure how this will change queue times. Queueing as a 5-man probably won't change much for you from what queue times are right now, but I imagine a 40-man team will be standing around Shattrath for quite a bit longer. I would go try it myself, but I unfortunately do not have 40 friends on the PTR. So lonely.