As you asked,
Would something like this work?
If Attack Value was 20, Level 2 Creature
5+((Random Number (2*2) to 15))
In this case 5+(Roll of 4 to 15 or Min 9 Max 20)
25% of Attack Value + ((Random Range(Level*2) to 75% of Attack Value))
DEF could be left a 0-Max Roll, or Use a Similar type roll.
Note May or May not want to MAX the Level, needs testing.
I am Adding Level as most of the Attack Value cones form the Weapon, and one would think the more Skilled would do a bit more damage with the same weapon as a Trained new Fighter.
This gives a large Range and with DEF working the same way still allows Chances for Misses when the Values of ATK and DEF are close. But also allows for a Strong Hit as well.
Right Now ONE side Moves and Attacks, then the Other.
Using a Combo of Move+Dex perhaps, each Figure/Unit Would go from Highest to lowest.
Attacking Force might get a +0.5 to the Number.
All Weapons except perhaps Daggers lower Initiative, Big Two Handed Hammers are Slow.
If a Figure Waits, to allow others to act it Loses 0.25 each time, it waits.
Mounted Units would get the Mount Move Bonus, as would Hasted Units.
Use Range Bands
Give each Ranged Weapon, and maybe some Spells, Range Bands.
At Short they have +15% to Hit and Damage, at Long -15% to both, the Middle is Normal.
But Have Different ands for Weapons, a Spear should be like 1-2 For Short, 3 Med, 4 Long.
Where an Short Bow might be 1-3 Short, 4-5 Med, and 6-8 Long,
and a Long Bow 1-4 Short, 5-7 Med, 8-12 Long.
Some Direct One Target Spells Might also use this.
Allow some Units to have Heavy Damaging Ranged Weapons, but Limit the Ammo.
A Spears, 1 or 2 Javelins, A Monster could have a Spine Attack but a One Shot.
Should be able to give to abilities as well, so Mana is not needed to use them.
This causes the player to have to make the choice when and where to use them.
Various abilities, and more spells would be great as well, but I feel the I Go, You Go is a balance issue to heavily in favor of the attacker.