The maps are only too big if you aren't using vehicles. I love the scope and size of these maps. And I don't think it's unbalanced at all... I mean, logistically yes, because one team has access to more vehicles, but that doesn't make it 'unfair'. If you have a defending team of people all playing as lone wolves, out for their own kills then yes, you'll get destroyed, but that's hardly a new thing. Any game that has vehicles involves a combined team effort to overcome. It's been that way in Halo, in past BF games.... A team working together can dominate with vehicles in the same way that a strong team defence can stop the vehicles from getting anywhere near them.
We defended brilliantly in the desert level with just ONE squad. One guy laser designating, one guy javellin rocketing and one support class refilling the javellins and we held back every single vehicle. The rest of the team were mostly assault and provided ground support and revives, plus this one engineer kept putting down anti-tank mines. It was an amazing game and just highlighted ALL this games brilliance for me, so I have seen no problem with the maps so far.