Deaths from guards/fort siege mobs (balaur or opposing race) do not cost you any AP or EXP. If you die to standard PvE balaur mobs, it is treated as a PvE death and costs you EXP only.
And yes, I had posted evidence a while back that clearly indicates that AP loss is determined by level difference. If you get killed by someone 10+ above you, the final AP gain for them and your AP loss is only 1% of the amount shown, so if a bunch of 50s show up to zerg you, it doesn't hurt very much. There is a penalty to AP gained for killing somebody more than 2 levels below you and it follows the same mechanics as PvE EXP does in this regard.
http://www.bluegartr.com/forum/showt...57#post3300957