This, large scale PvP in an beta has to be zerg,
Now if you use strategy an odious solution is to use multiple small groups to hit multiple castles at once, forcing enemies to respawn an longer distance from the primary objective.
This has already been done.
In addition you can use an blocking force to hit the zerg run then they return in small groups or one and one, yes this is very dangerous as you can be overrun but will rank in tons of kills.
It will obliviously be zerging and zerg has its place however it will not be the dominating tactic among skillful players.
Why not, if you don't want you can simple not play this pvp style, but you will still have this option...
Because it spreads the pvp population into too many activities.
If you like arena pvp there are so many games on the market i wonder why you join a three factions pvp game and expect it to change its gameplay.
Btw i played GW for quite a long time, its not that i dont like arena pvp, i dont want it to be HERE because this game has been designed in a radical different way.
Arena pvp might be more "skill based" but there is no strategy and gets dull after so many matches.
Open world pvp is a mix of tactic, strategy, skill, experience, creativity and luck and never gets old.
We did tons of small group pvp (4vs4;6 vs 8 etc etc) during the weekend, just dont go exactly where the zerg is but where the zerg gets its reinforcements
it was AMAZING, battlegrounds really are not needed for what you want!
You can play predador/hunter style as well. You don't have to engage in the massive battles, just watch the roads for careless adventures, set up ambushes with a couple of friends. Cyrodill do offers all those options.