Your player base is declining. I know this, because all of my friends and all of my guilds are saying the same thing.
Xp gain is too slow. Incentives are too little. Only some specific class/builds are working in Vet play.
Xp gain is too slow: it takes hours of game play to move the bar. Quest rewards are too little. Mob kills are arduous, and reward little.
Incentives are too little: VR3 to VR4...so what. The mobs, however, gain loads more HP. We gain...............nothing. No skill point towards a decent vet-based unlock. No power boost. No significant unlock of higher-tier gear. Nothing. Where's the incentive to do the ggggggrrrrrrriiiiiiinnnnnnnnnddddddddddddddddddddddd? You're missing the basic MMO equation here: effort must be met with reward.
Only some specific classes: "play the way you want to play" doesn't work into Vet zones. You. Can. NOT. Solo. Vet. Play. on any build, unless you take 2-3 times as long and use potions etc. There are maybe 2-3 builds in the entire game that can solo effectively...pre 1.1.2 nerfs, anyway.
THIS is where your efforts should be focused. The "oh, we're working on bots and gold spammers" excuse is old, and you've demonstrated insufficient progress to justify this.
I can't make this message clear enough: if you don't address more of what the players are wanting, and soon, you won't have to worry about bots and spammers any more because they'll realise there's no players to sell to.