Um... no. That's not really how it works at all. Or rather, if you are actually concerned about a singular event, that is how it works. Until your bonuses bring you into the critical range of potential success, you have a very small chance of success. And once you have a very large chance of success, further bonuses hardly matter.You have samurai 1 and samurai 2 locked in a epic struggle to the death(they are identical characters, both hitting the other on a roll of 11). Since each consecutive bonus to attack for ether will give diminishing margins of returns, the difference between +7 to attack and +8 to attack is very little in terms of the percent of hitting. However, The first +1 will give you a significant change in terms of success percent, as well as the first -1. This means that when samurai 1 and samurai 2 are battling, things like high ground(+2) can give up to a 20% or more improvement in your hit chances, while when Peasant 1 attacks Samurai 1 (DC18), having high ground and flanking (+4) will only give about a 9% increase to the chances of hitting. It doesn't really matter if the peasant has high ground or has good cover...the samurai is so much better than him that while something could happen and he could stab the samurai...it doesn't matter that much.
But my rejection of your assessment has nothing to do with the fact that a +4 provides a 15.8% increase in chances for that peasant and not a 9% increase you reported. My complaint is conceptual. When you have a battle challenge, you are going to be facing some number of goblins or peasants or something as to be actually challenging. Which means that while they might only hit on a 16+ and individually hit about 4.6% of the time, there are like 20 of the damn things, and collectively they are handing out about 1 hit a turn. If you give them a +2 bonus because of enchantment or some damn thing, they will be individually hitting on a 14+ and be squeezing out hits 16.2% of the time - which means they are throwing down 3 or more hits a turn. The danger of the enemy is increased by a factor of three. You get something very similar when you have an equivalent situation in d20 land.
Mobs of weak enemies that hit on obscure numbers always become radically more dangerous by tremendous factors when they get numeric bonuses to their to-hit rolls. That's just how swarms of attacks work.
But you are correct that with two evenly matched samurai that hit each other around half the time, having one of them get the upper hand, either offensively or defensively, is a big deal. While a powerful samurai attacking a weak enemy they will probably hit will not benefit much from an additional bonus.
-Username17
