Blizzard offered some details on balancing Wintergrasp Lake World PvP.  (source)

We’re hoping to get the zone into better shape in the next couple patches. Here’s a few things that should be coming in the next build:

• All vehicles should be despawn after the battle ends
• Demolisher and Siege Vehicle health has been reduced by 50-75%
• Demolisher and Siege Vehicle ram attacks no longer knock a player high enough to kill them
• Jet & Bomber health has been reduced
• Bomber damage has been increased
• Players in Bombers should no longer take damage
• Reward for holding the keep has been added
• The Goblin Workshops in the North and South now also supply players with land mines that deal bonus damage to tanks

We also hope to have a system for rewarding only players that participated in the battle working soon.