Well, if you and your players would prefer a "sliding" percentage to hit vs. a passive defense, here's a house rule I've used before - most recently for WFRP. I used it to experiment with the idea that the players could make most of the rolls in the game, freeing me to concentrate on story and narrative.
The PC's weapon skill is considered the default vs. a skill 50% opponent. The PC's chance "to hit" is then modified by the opponent's skill if it is over or under 50%. The quick little pixie with a 70% dodge is -20% for the PC to hit, the slow, unskilled Troll with a 45% parry is +5% to hit. If the player makes the modified roll, the PC hits, there is no defensive roll.
You can also use this for NPC attacks, just use NPC attack skill +/- 50% to modify the PC's defense skill. If the PC makes their modified defensive roll - they defend, it they fail, they're hit - GM rolls damage.
You can also use this rule throughout the game. NPC has a skill of 30% for Spot, then the PC rolls their hide roll at +20%, etc. The GM rarely has to make a roll.
I've only used this rule for games where skills are capped at 100%, there may be problems for skills levels over 100%. Also, I used this rule along with house rules to increase skills in 5% blocks, the modifiers are quicker if they're in +/- 5% blocks.
This is really just using the Resistance Chart option for opposed roll option from BRP, with the players making all the rolls and expanding it to include combat.