You’re forgetting a major factor though. Which is the natural movement of players.
So let’s say you’ve got that factor increase (wild speculation imo, you can’t really predict anything other than the fact that less alliance are likely to queue if premades won’t be possible), you’ve got the quitters to consider too.
Not all horde will keep queuing if the queue times increase. This will have a reducing effect on the horde queue times, which will bring it down again, and round and round it goes.
The queue times will only be as long as the collective tolerance of the horde will allow it to be.
Then you’ve got the ones chasing that peak honor per hour, even on the horde side. Once they go past their tolerance levels, they’ll seek to form WSG premades instead.
This is a good thing. It’s always better to seek out the social activity rather than the asocial one.
Also, you seem to be confused about something. The 5-man limitation is an increase from the solo limit in AV. It doesn’t affect other BG(s), such as WSG and the upcoming AB in phase 4 (probably arriving in the summer, hard to predict their early releases though).
Those BGs still allows the better social design of full premades possible for everyone.
As for why premades shouldn’t be segregated into a premade-only queue, see:
and you can read the entire thread for context.
These new changes only serves to make it harder, but it likely won’t prevent premades forming altogether in AV. It’ll definitely make full premades much harder to achieve reliably however.
The Russian pools are a problem nobody speaks about yet though, but they’ll grow into a much larger problem later on in AV once the gear disparity increases with t2, t2.5 and t3. Because their ability to form premades won’t be affected at all by these changes, due to their extremely small matchmaking pools.