Actually that won't fix the problem, because a crit: damage * (1+0.5), is only one multiplier among many. As a Rogue with an enchanted weapon I could have many seven-eight damage multipliers. Less crit damage (which guns already have) does not make much of a difference because all of those multipliers scale with the base damage of the weapon.
Here is an example
Rogue with Sneak Attack (x1.25), Blinding Strike (x1.25), 21 Might (x1.33), Fine Weapon (x1.15), Crit (x1.5), Damaging 2 Enchantment (x1.3), Two Handed Style (x1.1)
Let's say I roll 18. That becomes 18 * (1+0.25+0.25+0.33+0.15+0.5+0.3+0.1) = 51.84 damage. Dropping the crit multiplier to 1.2 only changes that to 48.24 - which isn't much difference.