Well the author's comment says it all:
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Since some of you might be curious to the DPS Calculations in the build...
Mangs vs 0 LR monster: 35,767
Infinity vs 0 LR monster: 28,097
Mangs vs 50 LR monster: 32,906
Infinity vs 50 LR monster: 28,097
Mangs vs 100 LR monster: 12,698
Infinity vs 100 LR monster: 14,892
Mangs vs Diablo Clone: 24,858
Infinity vs Diablo Clone: 24,445
Which translates roughly to: Mang's build is dogshit.
Most monsters at Hell difficulty will start with around 50 LR, so your DPS advantage is only slight. Whereas where it matters (broken light immune), self-wield Infinity has a DPS advantage.
Moreover, the massive -55% LR stack from Infy is effective from the first nova/static cast, whereas when your merc is carrying Infinity, you need to wait for the aura proc for the extra DPS oomph.
Lastly, Insight / Cure / Prayer combo on merc gives you massive survivability from 300 mana and 50 life regen per sec. The best I saw with Mang is 150 mana/sec. When you spam Nova at lvl 45, it burns 176 mana/sec, so you're quickly in the negative. RIP.