A good idea, but unfortunately you need a little more research in the way of enchant. It would be better to use an up'd kuku for your merc, it would completely own all pvm. 2 reasons to use kuku>08 WF
1. Fires Exploding Arrows
2. Pierce Mod
Enchant and Exploding arrows are godly. Enchant applies once when you hit the monster, and again when it explodes. So in effect, your doing double enchant damage. Also the explosion can hit monsters around the one actually hit, applying enchant damage there as well. Pierce will allow multiple monsters to be hit by one arrow, and exploding on each monster. So a monster can be hit by the enchanted arrow, by the enchanted explosion, and by surrounding explosions from pierce. Literally one enchanted arrow can apply enchant 2-15++ times per monster in a pack. Its really funny to see a bow enchantress take down all of eld's or shenks minions with one arrow, but they can be that powerful.
I really don't think this is all that great of a build however, as a bow enchantress would be better. Using prebuff gear, and then switching to a demon machine (the ultimate enchantress bow), and using an act2 merc with an infinity and maybe prayer or something, you can kill even fire immunes, always pierce and explode arrows. You can keep the same damage if you prebuff right, have a really nice tank with an act 2 merc, and kill everything. DM gives over 600 ar, multiplied by enchant, will allow you to hit most of the time. If ar is too low, switch some fire gc's to ar/life gc's
If you are instant in using a merc to kill everything, then at least switch its bow to a kuku, it will be much more powerful.
The one thing I really like about this build however is the dream helm. Using a dream helm and max light mastery +TS you don't even need an infinity for immunes. I think I'll make a guide based off of this fact