Combat Considerations

Follower

makes the game in the game more interesting by providing more NPC interactions
enables more tactical decisions in combat
adds more strategic decisions about which of the available companions has a better synergy with the PC
different followers add more variety
there could be quests with weak or overpowered followers

Evasion and Reflex

explains why are skimpy armors as good or better than bulky ones
more tactical choices: fast with low defense x slow with high defense

Evasion when attacked the first time

provides the opportunity for cooperation, e.g. fast companion with a light attack removes the evasion and distracts the enemy and then the PC hits very hard
rewards correctly used presence (when completely surrounded character with lower presence will probably get attacked only once)

Initiative based on Reflex

more benefits for the fast characters
on the other hand, it might be beneficial to attack last after the enemy cannot evade anymore
more varied enemies; very fast x very slow
the small randomness in the calculation of initiative should add more uncertainty and thrill while remaining mostly predictable, has to be calibrated well
very fast characters will be able to attack twice per round which would be totally badass

Chance to miss

more attacks would be necessary to kill the enemy, making the combat longer
it would not make it more interesting, could cause frustration

Regeneration

encourage boring waiting and evading combat until the attribute recharges

Critical Lucky Hits going through Evasion and Armor

some high-level enemies might be hard to kill
high-level PC with high evasion or/and armor will be practically invulnerable, this will keep the combat risky
different weapons might have different critical hit chances, providing more variety
there could be actions, perks, effects adjusting the critical hits probability
affecting both evasion and armor makes things simpler and easier to balance

Armor

Armor bonus added to hp

simple and clear
not mechanically interesting
hp gets ridiculously high

Armor as a separate bar

more mechanical possibilities
could not be fixed with potions, would require repair skill
armor repair skill would encourage adding crafting which I do not want to add
armors could be destroyed which would expose PC
but it would make the player lose an irreplaceable piece they might like

Armor as number subtracted from the attack

seems the most realistic
weak enemies would not be able to penetrate the armor, making fighting them tedious and pointless

Armor as percent reduced from the attack

weak enemies can still hurt you
armor and evasion are equal(!):
- 10 attack dealing 10 damage = 100 damage
- 50% evaded = 50 damage
- 50% armor damage reduction = 50 damage

Potions could be used on an ally

less realistic
enables more tactic or strategic choices (one character to focus on damage dealing and the other on support)

Potions are more powerful

potions are no longer a free action, which of allies use the potion is a tactical decision
they have to be powerful enough to be worth combat action
drinking dozens of potions was tedious and gamy and they took too much space in the inventory
tactical decision whether to wait and risk to use the full potential effect of the potion

Immobilisation (Stun or Entangled) results in an automatic Critical Hit

stun or entanglement became more powerful
provides an opportunity for cooperation, one ally immobilizing the enemy and the other dealing the damage

Weapon types

more weapons provide more motivation to loot and more tactical decisions