Currently both fighter and wizard are getting the same bonuses from tactics. That means that a wizard is able to control his offensive/defensive capabilities as good as fighter does. Suggesting to balance this equality to give melee classes advantage in melee combat over classes non-specialized in melee combat.

1. Buff tactic modifiers much for Fighter specifically to give this class at least anything special. I used to think this class is designed to be specifically melee warrior.
2. Buff tactic modifiers a bit for Monk, Weaponsmith, Barbarian, Beastfighter, Duelist, Chaos Knight. For them melee combat is primary.
3. Leave tactic modifiers as is for Bard, Paladin, Ranger, Thief, Assassin. These classes are meant to fight in melee but has other own ways of dealing with the world.
4. Nerf tactic modifiers a bit for Archer, Merchant, Farmer, Mindcrafter. Melee is secondary for them, that aren't meant to fight very well.
5. Nerf tactic modifiers much for Wizard, Priest, Healer, Druid, Necromancer, Elementalist. They just aren't designed to fight in melee.

So for example while fighter would be able to get berserking +16 to hit, +6 to damage and -15 DV wizard would get +4 to hit, +1 to damage, -6 to DV under the same conditions (star sign, tactics skill, DV/to-hit/to-damage under F4 setting. Currently both gaining under these conditions +8 to hit, +3 to damage and -10 DV.

I'd make tactic usage by non-melee fighters less proficient so in general they would lose more than gain while melee fighters could have their penalties lowered.

Besides giving an advantage for melee classes in melee combat it might give some use to [F2 - F4] and [F6] tactics for fighters since currently usually difference between these settings not that large.