[RPG] UPDATED Critical Strikes & Attack Bonus ][-

As of now, I have settled on (AB / 5) incremental increase on the Critical Threshold.

Since I allow characters to purchase Levelled-capabilities, like Attack Bonus, at one-higher than their current Character-Level, I've pushed the value back to +5 AB, which is purchasable at Character-Level 4.

Crit- | Attack Bonus-
20. | AB +1 -- +4
19+ | AB +5 -- +9
18+ | AB +10-- +14
17+ | AB +15-- +19
16+ | AB +20 <

So far, I have two very strong votes for a Critical Hit determination Chart-thingie.
--Looking at my Arduin book, I ... > sigh <
---What can I say, guys? This stuff is not attack-type specific; ranges from low-power 'paper cut' to 'body shredded: instant death'. I'd rather give weapons/attacks the power they deserve and have it pretty clear that getting shot by a Mk. VII Blaster is just absolutely going to ruin your day from the game-maths, rather than even Rolemasterean Effect Type Charts, as silly-fun as those are.

I've looked at the Avalon Hill RuneQuest Deluxe box; I've even broken out AFTERMATH!, and neither of them goes anywhere into that kind of detail.
--I'm afraid that if folks want that kind of detail, they'll have to write up their own charts or what-have-you.

[RPG] Critical Strikes & Attack Bonus-

Another of the issues that the LGS owner discovered when creating his character was that the cost of Attack Bonus is higher over the entire run than the much more flexible, Focus Points.
--He didn't feel that the One Round switch-out to re-allocate Focus was enough of a balancing factor to reflect the cheaper cost, especially given the fact that AB and Fo can be used in conjunction.

He and his wargaming buddy then offered slightly more complicated ideas to make Focus more finicky, such as requiring a roll to Maintain Focus, and so forth.
--While I think that is a cool idea, I'm pretty certain that the same net effect can be achieved without adding a recurring mechanism, let alone one that requires an additional roll.

Prior to his noting that mathematical error on my part, I had been contemplating the nature of Critical Strikes, and how I wanted character skill/ability/prowess to reflect more on their frequency than the simple 'dumb luck' of rolling a 20 on the die.
--I am currently thinking of the following, or something like it:

* (AB / 2) lowers the Critical Threshold

This simply means that more proficient fighters would benefit from more frequent Critical Strikes.

AB +2: 19-20
AB +4: 18-20
AB +6: 17-20
etc.

I still plan on revising the cost of both AB and Focus, but I am asking for your input on the matter of removing pure luck from the Critical Strike.

Thoughts?