1. Backfire
2. Interrupt of your choice
3. Ether Lord
4. Energy Drain
5. Energy Tap
6. Mind Wrack
7. Ether Feast
8. Spirit Shackles

It's extremely easy to beat a mesmer-based mirror if you know how AI works. To make a long story short it recognizes that Backfire is the best bet for killing you off and will almost always lead off with it. Here's the process you use to beat it.

Go into the battle with your trigger finger on your interrupt. As soon as he gets into range he'll start casting backfire, and at that point all you have to do is interrupt. Then use Energy Drain and Energy Tap. Chances are he'll use his interrupt on your energy tap, making him susceptible to the next bit.

Put Spirit Shackles on him and then cast Ether Lord. Keep using those two as necessary, and once you notice he's stopped casting spells start putting mind wrack on him. With it pumped up all the way mine does 100 damage a cast and you can cast it every few seconds. Just keep your mirror starved and keep wracking him and he's toast.

Coincidentally, this is almost the same build I use against monks in PVP :0)

Let me know what you think.