There were some changes made to Lake Wintergrasp in yesterday's patch which have influenced the standard strategy for the zone. The attacking faction still has the advantage, but the increased hitpoints for the exterior walls makes it harder to take the fortress from the sides. The horde in particular were fond of taking the back western wall and destroying the goblin workshop. This had the advantage of being close to the attacker's western graveyard, but far away from where the defenders respawned. However, this strategy only worked since the fortress cannons could easily be taken out by range classes. With the recent changes to the zone you can see how this won't be as effective.
Patch Changes that effect Wintergrasp Strategy
-Wintergrasp PvP vehicles have had their health increased.
-Wintergrasp Tower cannons have had their health increased.
-The Wintergrasp Fortress Exterior walls have had their health increased.
-The Fortress Keep door now has had its health decreased.
-The Orb is now instantly clickable.
This should slow down the pace of Wintergrasp a bit and make it so that 8-10min games happen less often. That's not to say Blizzard wants the attacking side to lose. The design of Lake Wintergrasp still favors the attackers and it makes sense to encourage the zone to change sides often. The problem was that the previous setup gave the attackers too much of an advantage and games were ending too quickly. The exterior walls and cannon health was increased to make Wintegrasp last longer, but the keep doors had their health decreased. It may take longer to get into the inner courtyard but once the attackers are there the game should be practically over now. This is especially true since the orb is now instant clickable and can't be defended by constant AOE attacks.
So what are the strategies for Wintergrasp now?
Catapults are going to be more handy for defending cannons from players. They've always been the best anti-personal siege weapon, but were fairly easy to destroy. The increased health should make the catapult less of a push over when facing groups of players on the ground.
Demolishers and Siege Engines are still going to be needed for taking out the attacker's workshops. The trick is to destroy the workshop and not just take control of it. Unfortunately, from what I've seen, defenders often move directly into the workshop instead of supporting the siege engines bombing it. This usually causes the defenders to take control of the workshop and prevents it from being destroyed. As a result when the attackers respawn they can easily retake the workshop and resume launching attacks close to the fortress.
There's no longer any reason to have aoe classes in the Orb room since its instant clickable. In general with the new patch there's more reasons for defenders to be fighting outside of the fortress. Basically once the attackers are in the inner courtyard the keep doors are so weak that the game is practically over.
The side walls will take longer to destroy and it should be harder to suicide attack the cannons on them. Walls should probably only be a target when there's no defenders outside to prevent attacks on the cannons. It doesn't seem like you can simply ignore defenders and quickly destroy the cannons anymore.
The front gates are weak compared to the walls now and should be a priority. The increased health on vehicles means they should be able to approaching the front gates and get a couple ram attacks off before being destroyed. Standing back and firing from a distance should only be done when firing in a tower's blindspot.
I think catapults are less useful to attackers now since demolishers and siege engines have more health. It used to be a problem getting vehicles into ramming distance and catapults helped defend the slower moving vehicles as they got into place. Now with the increased hitpoints I think there's less reason to bring catapults into the fray unless there are large groups of defenders outside the walls.