Realms Blackrock's activity at this moment.

[truthwow1]

I don't even know where the supposed problem lies, so I can't really argue for or against it. Do you or anyone else have a clear idea?

I can also only assume what might happen.
When gearing up on Blackrock is made even easier, means increased honor rates, several flushes a week, etc, then it's likely that all upcoming pvpers will choose Blackrock over the other realms that take part of the Battlegroup because of the obvious gearing advantage.
Ppl that wish to do PvE aswell would just make their character twice. One character on Blackrock for PvP purpose and a second version of their character on one of the other realms for PvE purpose.

Blackrock itself would be a realm with several design flaws. It would want to be a realm that mainly attracts arena players like back in the AT era but due to the gearing advantage towards the other realms it would attract mostly players that wish to do BGs.
The majority of Blackrocks population would consist of bored BG heroes that have nothing to do on that realm because due to increased honor rates they already purchased all the honor gear in few hours.
They would lack the motivation to start again from scratch on a other realm. Grinding all the honor on a other realm just to purchase furious gear while even better gear is available for free on Blackrock would only mean to handicap themself.

Donation would also go down.
Since every upcoming pvper would start on Blackrock there would be no more donations on BiS trinkets that are available for free. Donations on trinkets such as DV normal/HC or Solace normal/HC wouldn't exist.
Donation on highend HC trinket would also go down drastically because their normal counterpart, which is almost as strong, would be accessible after just one BG thanks to the high honor rates.

That should give you a little taste..
Some of the mentioned problems already appear right now.
If Blackrock becomes even less grindy than it already is then it would make these issues exponentially worse.