Physical Rain of Arrows - best 5 support gem combo?

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volanchik wrote:

Make a calculation. As I understood you cannot support your RoA with mana, so 2 gems is a must have: BM and smth to heal.

Your life leech: 20% from your max life pool per second. Assuming that you have enough damage with Life leech gem to get to the cap. So if you have 4k HP, your leech will be 800 HP per second. With vaal pact it will depend on your DPS.
Life on hit gives 40 * 0.75 = 30 life per target hit. Lets presume your aps is 3 and you cover not least then 5 monsters at a time. Your LoH will be 3 * 5 * 30 = 450 life per second. So, because we don;t know your build and gear it is up to you to calculate what gem is better for you.
But take into consideration that with BM RoA Life leech will cost less life to shoot then LoH, because of 1,3 multiplier on Life Leech vs 1,5 on LoH.
Cost per shot:
Life Leech: 18 mana * 1.6 (Conc) * 2 (BM) * 1.15 (Faster Attack or 1.1 F Proj) * 1.5 (AoE) * 1.3 (LL) = 130 life per shot * 3 aps = 390 Life per second
LoH: 18 mana * 1.6 (Conc) * 2 (BM) * 1.15 (Faster Attack or 1.1 F Proj) * 1.5 (AoE) * 1.5 (LL) = 150 life per shot * 3 aps = 450 Life per second