According to the ESO Build Editor, yes it does. I put 50 CP in Mighty and 50 in Master At Arms, and the calculation hint says "Tooltip Damage 1 = 9652 Poison Damage + 11% Poison + 18% Direct + 5% All = 13074 final"
It's not 100% certain that the build editor is accurate in that regard, but usually they are very accurate, so I'll assume that the answer is "yes".
Master at Arms is the most efficient way to increase sub damage.
The next most efficient way is to unlock the Tactician and Exploiter passives, giving you a 10% damage increase after a dodge roll, the inefficient CP you spend to unlock tactician would not yield a 10% increase in damage if placed elsewhere.
Since unlocking Tactician leaves us with 110 remaining CP to split between Mighty, Precise Strikes, Piercing, and Thaumaturge you’ll want to be efficient with those points and make sure you’re hitting jump points and squeezing out all the damage you can depending on your specific setup
Edit: @Reorx_Holybeard has done great work with the build editor and the only issues I’ve ever found with it have been irrelevant number differences due to rounding