These changes make me think of how the Marksman skill will be implemented, and how YOU want it to work. Do you want it to be like Oblivion, where even the biggest nub can shoot a perfectly accurate arrow at huge ranges, while somehow doing pitiful damage, or do you want it to flip completely, having you accuracy be pathetic at first and increasing as your skill does?
Option 1: Just like Oblivion but with much higher damage. If it takes 12 shots to kill as a Novice, it will take 10 as Apprentice, 8 for Journeyman 6 for Expert and 4 as a master. This will mainly effect stronger enemies as enemies that only take 2-3 shots to kill would take 1 shot as master, only giving you a 1-2 shot bonus over the lowest rank
Option 2: Damage stays the same or slightly increases based on skill level. If based on the example above, it will take 8 at Novice, 7.5 at Apprentice, 7 at Journeyman, 6.5 at Expert and 6 at Master.
The bonus you get for leveling up would instead increase you accuracy as well as give you some perks.
At Novice, your shot spreads quite wildly and is relatively slow.
At Apprentice, the spread is reduced and speed increases. You also take less fatigue damage from drawing the bow.
At Journeyman the accuracy and speed is further increased and you lose no fatigue for having the bow drawn.
At Expert your accuracy and speed is increased again and a reticle appears on your screen that shows exactly where your arrow is going to hit (it moves randomly in the "spread bubble" and compensates for gravity)
At Master your accuracy is perfect, your speed is even higher and your shots have a 25% chance of knocking the enemy back if they don't block it with a shield and a 10% chance if they do
(your accuracy, speed and fatigue don't make huge jumps, but increase smoothly from one rank to the next)
Option 2 will make marksmanship more believable IMO and still make ranking up worth it, but if you don't like it, say why