I don't see this changing much besides it making an artemis required to do a merc's job, while making the merc a further bane by disabling everything in one shot. Good gunners will only need 1 shot to annoyingly disable rows of components.
Broadsides are easily disabled now that it has two shots, a good gunner can disable a whole broadside in one go if he is good, with the penetration you might do damage somewhere else, but you won't be getting a broadside if you are charging them, if the enemy let you get a good shot on them from any other angle, their fault and should be punished. Dedicating a ship to doing just that will be a massive hit to your DPS. Also the Mercury is already being used as an approaching weapon.
Sure, art is harder to shoot, but toss lesmok in there for the faster missle, you get 3 rounds instead of 2 from merc, and net more damage than a merc with 3 hits. Then toss in burst at short range and yea, no. That's a terrible thought. You would have to nerf it's turning arc to that of a merc to balance it out.
You either didn't read the change log, in which case I'm realy mad at you, or I don't even know..
So, the equation for the total damage the Mercury does on armor with Charged rounds, which is what most people use when armor breaking with it: (75*1.5+300*0.2)*1.3 = 224.25 * 2 = 448.5 total damage with its 2 rounds.
And that is with a range of 3000 meters and an easy to shoot gun.
Now the changed Artemis on Lesmok as you said: (35*1.5+85*0.2) = 69.5 * 3 = 208.5
With Burst rounds: 347.5
(Do keep in mind that the current Mercury with normal ammo deals 345 damage to armor with its 2 rounds)
At 1500 meters with a harder weapon to shoot and need to make more shots count.
So you were saying something? I think this is a pretty fine number for something that fires at these long ranges, despite the arc and it retains a lil' bit disabling power.
The only time I liked penetration was when awkm made it so "heavy" components took 2 shots. Otherwise, you just get a dedicated boat disabling everything on anything that doesn't also have the same loadout, and a kill boat, which here would just be 2 or more artemis'.
Except a single shot Mercury with penetration and no armor piercing is useless against any boat without Heavy guns, and ships with heavy guns are now punished less cause it only has one shot that needs to be landed else you need to wait for a reload, the penetration is there to make up for that a bit. It no longer destroys both armor and components, you can not fully disable a Galleon's broadside in one magazine but you still have a weapon that has a massive role in approaching ships with heavy guns, can potentialy take out multiple engines and is still good at fending off enemy ships with heavy guns.
The only other change I could think of that didn't include penetration is lowering the Piercing further down to 10, basically what a single gatling bullet would do, take out the penetration and leave the 2 shots instead of 1.