Nerf gunners. The easiest fix is to add PvP modifiers to their skills, like x0.6 PvP damage to Missile Guide, Watery Grave, Juggernaut Cannon, Hemorrhage Shot, etc. This will only affect their PvP capabilities, leaving PvE intact.
Don't listen to people suggesting +20 enchantment, this is what introduced even more issues on Aion Lege*d. Folks started to cry and produce lots of forum topics. It's easier to enchant a weapon to +20 than a full armor set (5 pieces). This resulted in defensive classes being at a disadvantage. On top of that, when you enchant a weapon, you're getting more attack or magic boost; for armor, it only gives HP and physical & magical defense. It will make gunners more ridiculous than ever. Yes, give the gunners +20 cannons. Not talking about how you reduced the chances and amounts of enchantment stones that drop from Sauro and other dungeons.
Don't add any new dungeons from higher versions. This is a 4.6 patch. This is the one version that can endure years and years on its own. It has a lot of dungeons, more than enough. When new folk join our server, they expect it to be exactly what it says, and it says "official 4.6 build", not 4.8+. If somebody wants content from 4.8, then they can go to a 4.8 server.