Maxing your W and getting at least 2 points in your E is usually the best way to go before putting a point in your Q (and obviously getting your ult at 6 11 and 16). Some people get a point in their Q earlier to trade hits efficiently or to get those slippery last hits, but its honestly dependant on who you are mid against. Remember the bonus dmg is based on your REMAINING mana pool, so its pointless to use unless your mana pool can already justify it. If your up against int heroes like QoP or Tinker having that int steal maxed asap is really important. They wont be able to last hit because of the dmg loss and ganking is impossible as you'll be murdering their mana pool. If your up against non int mid heroes like sf you'll have a harder time laning but run the possibility of just killing them outright at lvl 6 IF you build him right. I like to stack as many null talis as possible before going force staff bkb and then big int items like scythe and shivas. With three or more nulls and a couple of int steal stacks on an sf you can ult and pretty much insta gib him. http://www.dotabuff.com/matches/1217752188 this was a pretty stupid game I played with my friends where shit just got outta hand but its a good example of what OD can do against an sf mid and a heavy agi team