Combat Modifiying Stats

Rules of Thumb based on Damage Formula
if your average hero has an ATK of 150 or so (200 at lvl 100) and is using tier 10's against tier 10's (165 ATK v 130 DEF), then the following are roughly equivalent in terms of damage, each doing about 7% extra damage:

+5 melee ATK%

+8 unit ATK (although I've never seen this as a mod for tier 10's)

+7 dam caused by melee

+18 Hero ATK

for PvP, this is probably about equivalent to 6% chance of double hit.

There is also a big caveat here in that we don't know the defense part of the formula.

Damage Formula (incomplete)
Currently only works for NPC monsters (presumably 0 DEF)

Dam = N * A/(1+D/A) * HA * XD

where:

ATK_MOD = 1 + round_down( spell% + ranged_or_melee ATK% + unit_specific ATK% )/100

A = modified_atk = unit_atk*ATK_MOD + unit_specific_ATK

N = number_of_units

D = opposing_unit_def

HA = 1 + (heros_ATK + equipment_ATK)/100

XD = 1 + ranged_or_melee_dam/100

e.g.'s of mods on items

"increases damage caused by melee units: 2" corresponds to increasing "ranged_or_melee_dam" by 2 for melee units only

Speed and Benefit
Note that each unit of hero SPD is +0.02 to unit SPD, so if you have a +0.10 thrower speed, it is worth 5 hero speed. Thank you saint for this page idea.

You need 10 speed on a unit for the front row to cross the screen and hit the enemy front row first turn, 12 let's you hit the back row from the front, and 14 let's your back hit the back. **This is wrong! It looks like 14.2 for back to back, so maybe 10.2/12.2**

Unit Allocation Formula
Base * (1 + Items/100 + Passive_Spell_Bonus/100) + Arena_Rank_Bonus