Any bros remind me how damage is calculated?
Is it converted, then added, then increased?
It depends on what are you doing.
Physical Damage + Armor
Generally physical damage is mitigated by armor. The more armor you have the less damage you receive. Because damage mitigated by armor is not damage - armor. The more damage is dealt the less effective you armor is. Shots from Brutus at merciless will really hurt anyone having only armor. This works both ways for you and enemy
Summary:
Damage
Physical damage - generally good and best for killing bosses. Supplied with skills can be also good for killing groups of weak monsters. Best use of it is like i said bosses and groups of elite monsters since high damage can mitigate armor and kill them quickly
Magic Damage - Fire/Cold/Lighting. Preatty straighforward + it gives you freezing/shock or burning stack when crit damage is dealt:
Shock - it adds 40% more damage to damage dealt. 3 Stacks of it is worth 120% amazing for single targets like bosses
Freeze - enemy is frozen and don't move or attack. Crowd control mechanic
Burning - enemy burns. It deals Damage over Time % of fire damage you dealt. Good for killing crowds and ton of weak monsters
Armor - It mitigates physical damage. Due to nature of mitigation armor is most
effective on packs of relatively weak monsters that could hurt you in group if they surround you.
Evasion - It gives you chance to evade attack. Something like dodge that completely negates attack values and you are simply missed. It is awesome stat for person taking out boss character since boss also will have to miss your % of evade. Coupled with shield it may make fight like Brutus easy. Evade has big minus though. Fighting one on one with enemy is its strong point but taking out groups of monsters at close range can be problematic. 5 monsters at close range can give you 5 attacks and with 50% evade chance you can get hit 2-3 times at the same time where in case of Brutus 0-1. This is why it is Ranger stat mainly. Because running with bow evades most of malee group attacks and evasion work best on single projectile attacks (that usually are only source of enemy damage for this class)
Energy Shield - Works like additional Life that regenerates after few seconds. It is good for withstanding few first attacks and getting to safe place but it will get you nowhere if you plan to receive a lot of attacks. That is why it is used for spellcasting classes and hybrids such as templar and shadow. Both of those hybrids (if they are build as spellcasting warrior and assasin ) need to stay alive either few seconds to cast spells or hit with poison dagger and move out of enemy range
Don't forget kids ! LIFE IS MOST IMPORTANT STAT to survive wraeclast. Just because you have mage it doesn't mean he doesn't need life to survive. At times there will be situations where you simply won't be able to dodge because for example whole screen will be filled with sparks.
It is good to mix some stats. Pure evasion/armor/energy shield may have problems in end game.