My ideal rotation

Thunder II
Swiftcast
Fire III
Fire
...
Fire
Blizzard III
Thunder II
Scathe
Repeat from Fire III

i keeps my damage up

What is extremely useful from Archer is Raging Strikes. This will increase your spell damage by 20%. It is a good idea to use this right before you start spamming Fire. Quelling Strikes is also useful for reducing the amount of enmity you are accumulating. If your tank is good then you may not need to use this.

From Arcanist you should equip Physick as healing spells are always useful to have. For your final ability I would recommend Virus as it has very nice benefits for yourself and the party by increasing damage for 10 seconds.