I've been working on a space themed fleet combat game called Skyward. I haven't worked on it for awhile, but I recently pulled out my initial ideas, and I was completely disgusted at my overly complicated battle mechanic. Here is the mechanic:
Attacking
Determine which units make successful hits
• Determine Evasiveness of defending unit
o Roll Evasive Die
o Add die value to Ship’s Evasiveness
• Determine attacking unit Accuracy
o Roll Accuracy Dice
o Add die value to Ship’s Accuracy
• If Accuracy value is greater than the Evasiveness Value, it is a successful hit
Determine damage
• Determine defense of unit
o Roll defense die
o Add die value to unit’s defense
o Add support value to unit’s defense
• Determine attack value
o Roll one attack die per successful hit
o Add dice values to total unit attack value
o Subtract shield penalty value for any hits that hit defending shield from attack value.
• If Attack value is greater than the Defense value, the unit’s armor level is decreased by 1 and damage is taken.
A little to complicated huh? Now I can think of many simple combat systems to use, but I want the system to support accuracy and attack strength. For example, a fighter will have a high accuracy, but it will have a low attack strength. In contrast, a capital ship will have low accuracy, but it will have high attack strength. Does anyone have a mechanic in mind that supports accuracy and attack strength but is still inherently simple?
Keep in mind that players can attack with many ships at once and target the same unit. When units attack together their strength is combined.
I'm thinking about using something similar to your second suggestion Quest. I think I will use custom dice like what are found in Heroscape or Risk Battlefield Rogue (defending dice will have four blank sides and two block/evade sides and attacking dice will have three blank sides and three hit sides). I will use the attributes of attack and defense. Like you said, the attack and defense values would determine how many dice the player rolls.
I still want to utilize an attack strength attribute, and here is my idea. Certain units could have specific attack dice that they roll. Stronger attack dice could have sides with multiple hits on them, and weaker attack dice could have less hits. For example, a capital ship attack die could have a side that deals four hits, and a fighter only has sides with one hit on them. Come to think of it, I could still use an accuracy attribute that is automatically incorporated into the dice. More accurate ships could have dice with more hit sides. For example, a fighter could have an attack die with five hit sides and only one blank side. However, the fighter can only deal one hit. In contrast, a capital ship could have a die with five blank sides (low accuracy) but have a side with 4 or 5 hits (high damage). What do you think?