It was never great to begin with. PvP should actually matter and be fun on a Red server if it's going to be worth playing.
1.)
Weekly Guild vs Guild tournaments with set numbers of players and equipment. Winners would get raiding rights for certain zones and other various prizes.
2.)
Don't allow guilds to zerg a zone.
3.) Give people a considerable amount of exp for killing other players (non-guildmates), which would be shared with groups (so that clerics and such still benefit). Every time a group kills a legal target, the whole group would get a "kill point" and these points could be traded in for monetary/item rewards. This provides incentive for casual PvP and an alternative to PvE as a method of leveling and getting loot. Obviously you would have certain rules in place with this so that it wouldn't be exploited by friends killing each others' alts constantly.
4.) Rework/balance the combat mechanics of the server to make it more interesting, less tedious, and open to every class and various group setups being competitive.