I think by now everyone knows that balancing the Vampiric abilities and passives insofar as how they work in Cyrodiil needs to be top priority. There are, however, other issues that need looking at:
1. Guesting/Switching Campaigns. I'm putting these two in the same category because they are leading to similar problems, namely the zerg-fest where a large group guests on a campaign, rolls the map, and then promptly vanishes. I know you've got a fix coming for the campaign switching by making the price tag higher, and the sooner you do this, the better. But that's not going to stop the guesting issue. I can see a couple of ways of dealing with the guesting issue: 1) guesting should also have a price tag (albeit I don't believe it needs to be as expensive as actually switching campaigns) or 2) put a hard cap on the number of guesters that can be in a campaign at any given time and base that hard cap on the total population in the campaign - thus, guesters logged in should never outnumber those for whom the campaign is their home (so if there are 20 Dominion players logged into a particular home campaign, then the number of Dominion guesters can not be more than 20, etc.)
2. The Emperorship. I cannot believe you intended the Emperorship to be farmed. This has got to stop. A very quick and easy solution to this is to simply make the past-Emperor bonuses ONLY viable in the campaign in which the player achieved Emperor status. This one simple fix would solve the "temp switching campaigns to earn Emperor so you can have the past-Emperor bonuses and then leaving" problem we've got right now. Thus, if someone became Emperor in Auriel's Bow, the only time they receive the bonuses is when their home campaign is Auriel's Bow AND only when they are logged into Auriel's Bow and playing.
3. Home Territory Bonuses. Right now, there simply aren't enough benefits for players to want to hold onto their home territory (I'm not talking about the entire map here; rather, specifically referring to each factions "home" territory on the map). The solitary bonus for holding all keeps just isn't cutting it. I suggest that each faction's players should receive bonuses when fighting in their own territory and for holding onto the keeps and resources in that territory. Note that these would exist in addition to the bonuses already in existence.
First, add in some bonuses that are present when a player is somewhere within the boundaries of their character's faction's territory - simple offense and defense bonuses should be fairly easy to implement. The minute the player goes into enemy territory, those bonuses vanish. Some of these bonuses could be tied to how many resources and keeps the faction is holding in their home territory, and some bonuses I think should be independent of that (meaning that even if a faction has lost control of their territory, they should still have some bonus for being in that territory)
Second, give additional bonuses to players who are inside one of their faction's keep's territory. So perhaps the home territory offense/defense bonus is simply an extra 2-3 percentage points on top of whatever the current home territory bonus is when fighting anywhere on the walls or inside keep territory.
Third, these bonuses should increase the longer a faction holds onto its territory (up to a set max, of course). So, as a quick example, A Covenant character has a flat 5% bonus to offense/defense any time they are in the Covenant's home territory. If they control all of the keeps and resources in the territory, then perhaps they have an additional 5% (and this percentage could fluctuate based on how much of the territory is in the faction's hands - lose one keep, and perhaps you lose 1% of the bonus). This gives them a potential 10% bonus for being in home territory and controlling said territory. Then, if they are fighting on the walls of their keep, perhaps they get an additional 3% on top of whatever other home territory bonuses are currently in place. Thus, a potential 13% if the faction holds all of its territory, or a minimum of 8% if they hold none of their territory.
The idea is to encourage players to push harder to defend their home territory - and provide real, tangible benefits to doing so.
4. Siege Weapons and NPCs. First, please stop having siege weapons degrade simply for being deployed - I grok that you want them to be a money sink for AP. I've got no issues with weapons degrading when they are in use. But it should be possible to set a siege weapon up and leave it there, and not have it slowly degrade until it is gone. This would allow folks defending keeps to put siege weapons in place and have them ready to go for when they are needed. And second - right now the Siege NPCs are simply useless - they are a waste of AP. They don't live long enough to actually be of use. So please give them a buff of some kind so that people don't feel they've wasted their AP on the purchase. Siege NPCs should also not degrade - meaning it should be possible for them to be placed and left there indefinitely until they are killed by an enemy.