How do you fight high armor with a low ST character?

[bluekitsune13]

I play with miniatures, so I've been rolling up a few characters and playing around in the system. I have some Warhammer figures, and I'm trying to figure out how to represent them in the system.

What I run into is you'll have these heavily armored knights that are also very skilled. This means they will have a high DEX to account for negative modifiers for wearing armor, but I also want them to have descent STR to be able to do good damage. Obviously these warriors will be fewer in number than other weaker characters. Then you have your rift-raff units like goblins who have low STR. If a Goblin can only even do 1d of damage, but he's attacking a warrior wearing plate that blocks 5 or 6 hits, how can he even do damage?

In another thread I was asking about hand to hand combat. It would make sense if in that situation that 2 or 3 goblins could try jumping onto that armored warrior and just taking him to the ground. Still, their daggers wouldn't be able to pierce his armor either.

Unless I'm missing something, if you just walk though some Goblins in plate mail you are invincible. Unless they get lucky with a crit or something, if they only roll 1d for damage, they can't touch you. I was thinking of maybe house ruling something where you can trade in a DEX bonus for a plus to damage. This would represent a sneak attack, or literally just piling on a downed enemy and stabbing for the joints in the armor.

I thought that any time you would gain a DEX bonus for an attack, you can forgo that bonus to gain that bonus as extra damage. So if you attacked a downed fighter, you would normally hit at +4DEX. If you wanted to use your regular DEX, you could add 4 to your damage roll. This means that you have a more reliable way of dealing damage to armored fighters.

I haven't tested it out, but it would be thematic for goblins and ratmen, and other small horde creatures.