Perhaps you're approaching it incorrectly. As a duo, you shouldn't be getting wiped out since most classes are capable of soloing mobs with the gear that's generously provided. You just need a partner to take down the 3 bosses that hinder progress NOT IN MENTOR since experience in the instance gets diminished (the first, the statue, and the horse bosses) making it essential to clear the entire instance and ensure you're in normal mode using all available exp buffs.
Afterward, you might tackle Rentus with a similar strategy. Some tougher enemies provide significant exp—just need to hunt them down because the ordinary ones aren’t worth much. If you can manage to defeat the first and second boss, more mobs will spawn. Also, watch out when they rage.
If that doesn't suit, consider quests such as the mithril repeatable ones in ingi—or if repetitive tasks aren't your thing, engage with normal quests that offer 5m xp each.
By the way, if you're looking to enhance your Aion experience more innovatively, I've been part of the Aion Riftshade beta and it's fantastic. The setup is different with improved features and active GMs, making leveling up a totally new thrill!