Thats the thing tho, if there is a zerg going around the middle zone its not really that hard to avoid them tho, the map is pretty big and you can avoid a zerg pretty easy if you havd awarness and dont always run down the main paths.
The best thing about wvw is there are so many things you can do, the possabilites are endless, you can solo gank, you can do supply runs, you can fank zergs with lesser numbers, you can bait people away, you can setup ambushes, hell in one of the beta weekends i had me and 3 friends standing in some sewers because a massive zerg came along, we ended up underneath them while they had a big fight and they were standing on these grates above us, we could do our aoe spells on this grate and we were killing people but they had no idea where we were
The thing with new mmos is a lot of people will always want to stick together in a zerg, the same thing happened in warhammer, i remember at the start there were zergs of like 1000 peolle running around together because it just snowballs, the problem in that game was most of the zones werent designed that great so it was harder to avoid the zerg, but in gw2 there is more free space off the road to allow you to avoid the zerg. But after a month or so (abviously after a lot of people quit) it became more about guild fights and the zerg pugs would get owned if they didnt have sme kind of organistion or leadership, so it became more spread out and had a lot more tactics. Of course you still had zergs running around, but you could avoid them most of the time because they are predictable, there like headless chickens. thats not to to say pugs or solo players dont have a role to play in wvw, becuase obviously there is stength in numbers, so when it comes to taking down big objectives like stone mists, you need the pugs and 'the zerg' to do it if its heavily defended, but the way this game works if the other servers just had one big ball in all the maps for example you could just avoid them and take objectives while they are zerging, they should have to spread out to defend properly.
Come to think of it, its a good thing there is a cap to wvw zones, if i made videos at the start of warhammer i could show you a video of the biggest zerg you have ever seen, one a lot bigger than anything in gw2, i stood on a keep wall open mouthed as they streamed in for a good 10 minutes, laughing with my brothers at the amount of people there was!
Also its worth noting there is a cap the amount of people skills can hit, im not sure about the cap on freindless buffs as iv seen guild all with speed buffs, but enemy spells are capped at 5 or 6 afaik.
Ergh, i said i wouldnt write this much on the ipad, oh well..