I believe that the ability to turn off cross realm should be added so that you only queue with players from Icecrown , it makes no sense that players gearing by playing the game get matched with players from blackrock which they get instant 80 and relentless gear from the get go, that's a big disadvantage and to be honest spoils quate a few the mood to play when you know you are most likely to be put in a match against them.
Would it make any difference if you were facing Icecrown players with similar gear level instead?
Of course it would they wouldn't be geared with full pvp , In icecrown you don't get to buy weapons, off hands and even trinkets with honor and that makes a big difference.
That would make battlegrounds even worse.
1) Longer waiting times
2) People on Icecrown are usually full geared anyway and if not, they are quite familiar with their class because they levelled it, so they know what to do. On the other hand, there are many people on Blackrock who just want to try some class but they don't know how to play it properly so even with good gear, they are quite harmless so you have chance against them. If you would meet only experienced people from Icecrown who got their gear by ranking, you'll get completely destroyed much faster, but with longer que time
Really 251 ilvl players make you sad? If anything You should be crying about full premades with gear 270+284 ilvl that have twice more power than rele blackrock players and they often stand at GY for full 30 minutes duration.