If you're a high pvp rank and use pvp stuff, mages can have over 4k hp, so they aren't easy at all for rogues, especially if they are frostmages (fire mages are a lot weaker in pvp vs melee classes).
Always start dueling rogues with mana shield on.
When the rogue goes for stealth at the start of the duel, just use Arcane explosion (rank 1) continuously to detect them. If you're good in making this, you should detect them an instant before they can attack, then use frost nova and blink away, and poly them. If they use the trinket to unpoly and vanish again, repeat the same strategy as before, and poly again.
Keep your mana shield active casting it often.
If they sap you, use frost nova and blink out when they damage you, then poly / start nuking them (if you're quite fast and far enough from them, their kick wouldnt stop your polymorph). Use frostbolt as your first attack, even if you're not a frost mage, cuz slowing them is very important. If you're a frost mage, you have the ice barrier option, use it. If you are in extreme need, use cold snap to reset the cooldown of your frost abilities so you can use nova / ice barrier again.
If you can play mages, its very difficult to loose a duel against a rogue.
If you're a human mage, just use perception at the start of the duel and pwn them easily.
