With the reductions in LoH coefficients in the next patch for several CM skills, life steal becomes more and more appealing. What I wanted to do was figure out when it is more beneficial to use LS vs using LoH, so I added a couple features to my spreadsheet. Now I am able to track the total number of hits from all sources, which are then multiplied by the respective spell coefficient, added together, and divided by the run time to come up with a Procs Per Second (pps) number. This procs per second is the effective LoH gains per second, so if your pps=1, you gain your full LoH every second, on average.
Based on a 60s fight, the pps of the twister and meteor builds ranges from 1.05-1.4 using my default stats of 1.5 APS, 40% crit rate, 16 APonCrit. The effective weapon damage per second ranges from 330% to 380% depending on stats and builds. Better stats will yield higher effective weapon damage but I feel this is a good starting point for the discussion. Also note that all Life Steal in Inferno is reduced by 80% so if you have 2% Life Steal, you only gain 0.4% of your damage done as life.
The resulting equation for 1.5 APS, a 3.5 effective weapon dps and 1.15 PPS is
Total LoH = LS% * Char Sheet DPS * 0.4
and is derived below for anyone interested.
So if you have 20k char sheet dps, the Blood Magic rune of 1.5% Life Steal is about equivalent to 120 LoH. If you have 50k dps it equates to 300 LoH, and at 100k it is 600 LoH. Remember, these are still just approximations so around those DPS ranges there aren't expected to be any significant differences between those LoH and Life Steal values.
There are several ways to use this equation. One is that based on your current dps, you can determine if trying to switch from a LoH weapon to a Life Steal weapon is a good idea or not. Or you can just see how useful Blood Magic rune is with your current gear.
It is worth noting that these calculations are done assuming there's just 1 mob present. I use just 1 mob because I feel that is the main concern of CM wizards, namely being able to stay alive and fight against just 1 mob like a boss, keywarden, or rare elite. Both LoH and LS scale with number of mobs but I haven't looked into how they scale. For those who are interested in multiple mobs, I encourage you to try out the simulator to see how the pps and weapon DPS change.
From my simulator thread:
Effective DPS = Weapon DPS * Char Sheet DPS / Attacks Per Second
Life Stolen per second= Effective DPS * LS% * 0.2
Life on Hit gains per second = PPS * Total LoH
So for the two life gains to be equal we have
PPS * Total LoH = Effective DPS * LS% * 0.2
or PPS * Total LoH = Weapon DPS * Char Sheet DPS / Attacks per second * LS% * 0.2
Using 1.5 APS, 3.5 weapon DPS and 1.15 PPS we are left with