First off, let's begin by stating that WoE may or may not be broken. I won't give my opinion either way on the matter. What I'm hoping to emphasize is that WoE can be a lot more than what it currently is. Here are some suggestions that have probably been stated before:
1. Remember when castles had no owner on the first WoE of a server and they were just full of MVPs and monsters? It was craziness. It was the closest thing to a pvp server iRO ever had. I think one castle should be randomly attacked by an NPC or Monster guild during WoE. Player guilds can try to hold against that onslaught. However, if the player guild loses the castle, they and other guilds can then fight through a raid-like experience to take it back. The NPC characters can drop useful items like yggs and condensed white bundles. Maybe not exactly this, but something like it would be exciting.
2. It's supposed to be a guild war, but I often just see one person holding the castle. Maybe beef up WoE guardians to level 178. Make them able to see cloaked characters.
3. Castle rewards. Are castle boxes still dropping low level gear? Maybe it's time to think about new rewards for castles? An NPC with one guaranteed upgrade per day until +10 would be nice. NPCs that give a bunch of different buffs and +10 to all stats for leveling. Free warps to everywhere. You could even make these perks appear based on the castle's investment status. They would obviously disappear during WoE. I believe little things like this, people will have fun fighting over.
Just some thoughts.