The correlation between xpm and Hero Damage is 0.76. The more xpm, the more Hero Damage, and vice versa. But some values are higher than expected, some are lower. Efficiency is a difference between the value of Hero Damage depending on xpm (blue dots) with respect to the expected value (red line).
Efficiency
Zeus 296.4254
Tinker 258.6765
Spectre 239.7004
Techies 225.0400
Venomancer 217.3093
Arc Warden 215.1529
Bristleback 191.5076
Ember Spirit 179.2545
Pugna 171.7729
Sniper 152.9434
Warlock 137.1710
Skywrath Mage 124.7519
Queen of Pain 120.8371
Necrophos 119.7871
Witch Doctor 117.7217
Muerta 116.1571
Clockwerk 114.3930
Timbersaw 111.8474
Viper 94.2459
Gyrocopter 89.8495
Axe 89.3024
Medusa 88.5910
Huskar 87.8145
Legion Commander 85.2463
Shadow Demon 84.0532
Enigma 78.4925
Outworld Destroyer 74.7794
Jakiro 74.4345
Razor 73.0172
Leshrac 71.8817
Phoenix 65.3509
Clinkz 63.5175
Silencer 44.1116
Void Spirit 43.8566
Nyx Assassin 37.7190
Puck 36.8670
Ancient Apparition 35.6230
Sand King 34.7526
Monkey King 28.4291
Shadow Fiend 27.6124
Lich 25.7005
Snapfire 23.9301
Death Prophet 23.3797
Rubick 23.3598
Underlord 23.3118
Bloodseeker 21.7637
Dark Seer 20.9906
Dark Willow 16.2965
Winter Wyvern 15.8300
Ursa 15.7282
Earthshaker 8.9627
Enchantress 2.3269
Crystal Maiden 1.8266
Elder Titan -0.0998
Weaver -0.8658
Drow Ranger -1.4614
Keeper of the Light -4.7515
Phantom Assassin -5.3079
Hoodwink -7.4194
Shadow Shaman -12.4560
Windranger -13.6496
Beastmaster -14.5982
Templar Assassin -17.2975
Invoker -19.4412
Terrorblade -22.9995
Primal Beast -25.2373
Pudge -26.4744
Grimstroke -26.6184
Storm Spirit -28.2313
Pangolier -28.3627
Ogre Magi -30.4797
Wraith King -33.2071
Batrider -33.4689
Bane -34.2094
Sven -36.1659
Chaos Knight -38.4773
Phantom Lancer -38.5732
Earth Spirit -39.6189
Juggernaut -41.2374
Disruptor -41.3561
Dawnbreaker -44.6557
Centaur Warrunner -48.7137
Tiny -48.8021
Chen -48.9917
Oracle -49.0299
Omniknight -49.3618
Tusk -53.8798
Kunkka -56.0139
Troll Warlord -56.9750
Bounty Hunter -58.3933
Luna -60.6563
Treant Protector -61.8576
Visage -68.0363
Marci -68.4090
Lina -68.8197
Dazzle -70.0509
Abaddon -72.6446
Vengeful Spirit -73.1444
Morphling -73.6763
Mirana -74.2977
Mars -75.2216
Riki -76.7697
Nature's Prophet -82.2365
Alchemist -84.0979
Meepo -84.5741
Dragon Knight -90.5451
Tidehunter -93.9061
Lion -95.7996
Lifestealer -95.9893
Undying -102.8797
Doom -108.2836
Lone Druid -109.7280
Brewmaster -111.9409
Naga Siren -112.5076
Slark -125.8337
Lycan -128.3174
Spirit Breaker -133.9444
Broodmother -155.9622
Night Stalker -158.0807
Faceless Void -164.3363
Slardar -170.8857
Io -171.8228
Magnus -190.2485
Anti-Mage -191.0172