If you plan fighting against W on a PvP arena, 4 skills are enough:
Crippling Anguish
Conjure Phantasm
Clumsiness
Leech Signet (Healing signet interrupt)
If you plan to include Rangers among your potential targets, then take Spirit Shackles as well, otherwise pick Drain Enchantment.
Finally, to be able to do some damage against casters, include Arcane Conundrum with Power Drain.
You'll need at least 13 on illusion and a 20% illusion recharge bonus.
Add your res sig, and you're ready !