More than a Game
Hm, it seems like a lot of us are having trouble with these monsters. So am I.
For those who have successfully beat one of these, perhaps we can help each other out? I'm a level 54 Striker (Char page is in the AQ Char page slot-- my stuff isn't that updated, but that's because I've been busy elsewhere. Anyhoo...), and here's how I beat the level 65 Nefadon (10 levels ahead is quite a bit)
Firstly, observe that the monster has 1000+ HP. It has a three hit ranged attack, which is devastating, and a one hit attack (about 1/3 of the 3 hit attack).
The first thing you'll want to do is minimize your Ice resistance. I sat in my Heavy Gunner Armor with a Network Deflector. There probably is better, but that was the best in my inventory. If you found a lower Ice resistance combination, please share? Thanks :) My weapon was the VGB Mark, but you should be using the Shimmering Axe (lv 55.)
The 3 hit attack deals about 50-70 damage, depending on whether there was a LS or not. And that was at 70% Ice resistance. Basically, all I did was spam the Power Punch attack, and that dealt from 70-100 damage a turn. That'd take about 11 turns to take down the monster, so that's about how long you'll have to survive.
Potions would be vital to success. I used 2 in my battle (healed about 250 HP), and one healing spell (healed about 150 HP). I admit, it took a heck lotta luck to win one battle, but it did work. Again, if any of you have a better strategy that's fairly consistent, please share. Thanks, I'm sure it'll help us all. :D