20 hard points in Strafe and Valk
1-15 in Multishot (enough to get a slvl15 Multi after +skills)
1-9 in Pierce (enough to get a slvl9 Pierce after +skills)
1 in Freezing Arrow
20 in Lightning Fury
Equip an Upgraded Shael'd Riphook, Cleglaw's Gloves, Blackhorn's Face, and Cleglaw's Pincers. That'll give you 75% Slows Target and knockback. Between the two mods, you'll be pretty much invincible while strafing (everything will be so slow that the knockback will keep it away from you forever). A Shael'd Riphook only needs 10% more IAS to hit the 9/2 Strafe Breakpoint, which is realistically as fast as you're going to want to go.
For your belt, either wear Nosferatu's Coil (nice leech, 10% more slows target, and that 10% IAS that you need), or else wear Razortail to give yourself 100% Pierce.
Between you and your valk, you should take down non-PIs in a hurry. Against PIs, switch to Lightning Fury (at this point, Razortail comes in really handy for that 100% pierce).
As an alternative, skimp on the Valk and ignore Lightning Fury entirely, and instead max Cold Arrow and Freezing Arrow to make a Strafe/Frostmaiden hybrid. Between your 75+% Slow and the cold damage, monsters will be moving at an absolute crawl.
As far as armor, helmets, ammys, rings, and boots go... use whatever. I'd recommend Kira's for the CBF and the Resists (you'll still want to max your resists), and Fortitude makes a phenominal strafer armor, but other than that just use whatever you want.
Also, and this is VERY important- *DO NOT* put any Slows Target gear on your merc. If there are two different people with Slows Target gear hitting the same monster, it causes *HEAVY* desynch, which is a very bad thing. If it seems like things are desynching out the wazoo, find out if anyone in your party has some Slows Target gear, or else some Slows Target on their merc.
Also, for the same reason, tell Necros you adventure with not to cast Clay Golem, and don't use the Clay Golem charges on Stone. The slow from Clay Golem is just like item-based slow, and will cause massive desynch.
A good merc suggestion would be Holy Freeze + Reapers Toll. If you think things are slow after you hit them, wait until they get Frozen and Decrep'd, too. It gets downright GLACIAL.
Also, this character downright abuses Baal runs. One hit with that much Slows Target will break Baal's AI and cause him to just sit there and use standard attack until he dies. No teleporting, no cloning, no mana-burn-hosing, no knockback-cold-wedge-thing, nothing.
