I just tried a shootout Maarek + Markmanship vs. a noname B-Wing at range 2.
First I used the Maarek with his actual ability. I used Markmanship as action once the shields of the B-Wing were gone.
I repeated this scenario for 10 times.
I must say that the B-Wings are brutal in a shootout. Maarek lost every time. It was close in a few battles when he was able to burn through the shield and actually had the chance to use his ability - but then he rolled a [blank] [hit] or a [blank] [eye] ... and the B-Wing was able to evade those single hits and blasted the last 1 ore 2 hull the Advanced got left at this point every time! A B-Wing sure is the most difficult no-name opponent for Maarek. Its worse than a X-Wing.
Then I tried the same scenario using the modified ability. Again 10 times; this time Maarek was using Markmanship every time he attacked, so no focus left for defence. In this scenario Maarek won 4 of 10 battles. In two of the 4 wins it was really close, while Maarek had only 1 hull left. It happened only once that Maarek was able to produce a natural [crit] and a [eye] and the B-Wing failed to evade one crit. He often rolled [blank] [hit] or [hit] [hit] or [hit] [eye] ... so the hits were divided between shields and hull.
So I must say it was fun to test the modified Maarek and even if he would be good especially against B-Wings, or better: he would have a chance against a B-Wing. Putting it all together I feel that an ability like this is far from being overpowered but its fun to play with the tactical options which would come with it. And even if Maarek never will have this ability, I really hope there will be an Imperial pilot with exact this ability.