Critical Mass is a Wizard passive that causes a chance of reducing cooldowns by 1 second everytime a critical hit is dealt. The in game explanation is, well, extremely poor and rather unintuitive as a result. There's little indication what DOES and DOES NOT proc this passive skill, and what the best skills are to utilize this ability. I've done some research into this skill by smashing high HP zombies with a toothpick, 2.0 Attack Speed and a 33% Crit Rate. I used a timer to time cooldowns for Diamond Skin and Slow Time.
Will it Proc?:
Magic Missile: YES!
Shock Pulse: POORLY! I tested Living Lightning and the default Shock Pulse. This skill is extremely odd - it does proc critical mass but it does so very, very rarely. With my setup, it procs 1 to 2 times every 20 seconds - give or take.
Spectral Blade: YES! Furthermore, the DoT on Deep Cuts rune ALSO procs. This makes this skill arguably the best one to proc Critical Mass.
Electrocute: POORLY! Tested Lightning Blast, Arc Lightning and the default version. Works very similarly to Shock Pulse and its variants, but seems to proc a bit more often. I get between 1 to 4 procs every 20 seconds.
Ray of Frost: YES! Yup, the beam move procs - meaning it crits. Try it out for yourself, it's actually the skill that arguably procs the most but is limited by AP.
Arcane Orb: YES!
Arcane Torrent: YES! Arcane Mines also procs the way it's supposed to.
Disintegrate: YES! The main beam procs, also relatively quickly. The AP cost means it's hard to get more than 2-5 procs for a beam that drains all AP, but testing with a group of 5 zombies got 16 procs in one beam (w/ Chaos Nexus). As noted, the mini-beams from Chaos Nexus also proc.
Wave of Force: YES! Not very helpful though.
Energy Twister: POORLY! I threw up a Wicked Wind twister (doesn't move) and for the 6 second duration I saw between 0-2 procs, and the 2 procs is VERY rare. These stack though - 3 twisters in one place gave me 4 procs once.
Hydra: NOPE! None of the Hydras proc. So sad - but increasing crit rate increases DPS and Hydras draw damage straight from the DPS stat.
Meteor: YES! The meteor strike, the molten leftovers and Meteor Shower all proc. At best, I've seen a single meteor proc 3 times. I blasted a mob with 3 Star Pact meteors at once and got 10 procs.
Blizzard: POORLY! Blizzard can indeed proc - but it seems to again do so in the same manner as Energy Twister. It usually procs about 1-2 times per storm, and Blizzards don't stack.
Ice Armor: YES! This surprised me. The Frozen Storm rune will, for its 3 second duration, proc. By continuously using the rune, I got it to proc 4 times in 10 seconds.
Storm Armor: NOPE! The Storm Armor's built in counter, Reactive Armor, and Shocking Aspect all do not proc. Shocking Aspect, as another proc ability, was extremely difficult to test, so I am not 100% sure. After testing, I am reasonably confident it does not proc.
Magic Weapon: NOPE! Venom was nerfed for a reason.
Familiar: NOPE! Again, a shame.
Explosive Blast: YES! But not likely to be a useful proc tool.
Archon: YES! All Archon abilities that do damage will proc.
Best Proc Ability?:
My procedure was that I activated Slow Time against ONE enemy, then started spamming the skills that were reasonable contenders for the best proc ability.
Spectral Blades w/ Bleeding Rune: 9.27 second cooldown (originally 20 seconds). Spectral Blades w/o Bleeding (since Healing Blades is very useful): 14.46 seconds (originally 20 seconds).
Ray of Frost (Tested with the 12AP Rune and Arcane Presence; INCLUDING time spent recharging AP): 8.8 second cooldown (originally 20 seconds). Best time was 6 seconds long.
Conclusion: Spectral Blades w/ Bleed is the best w/ multiple enemies. RoF for single targets. --- Megido! Megidola! Megidolaon! Sine! Cosine! Tangeton!