My concern about the Polaris speed is that it was designed as a patrol vessel, which is the traditional Corvette role. Gunboats do not usually fill that role. The role of a gunboat is usually to attack much larger vessels. Think of the WWII era PT boats. It's just an unarmored speedboat with torpedoes on. Dangerous as can be for its crew but punches way over its class.
Corvettes have traditionally punched best below their class. They use their speed to chase down smaller ships and dominate them. So for instance, the best representative of this today is the US Littoral class combat ship. It is not a "ship of the line". It's made of aluminum and so is very fast, but it cannot engage even the smallest of frigates. Instead, what it can do is be where no frigate can be because of its speed, and so it is a true patrol vessel. Littoral class combat ships were designed to hunt pirates in much smaller vessels and it's chief distinguishing feature is that of any true Corvette--it is FAST.
What CIG did when they created the Polaris was broke the mold by giving it serious torp capability. That is what makes it able to punch over its class, but it can only do this from great distance and needs to cut and run against any real ship of the line. You would not for example, want to pit it against a Void Bomber's spinal mounts, for it would not take long for the Vanduul Corvette class to cut the Polaris to ribbons. Yeah, a Polaris should be able to kill a Void Bomber, but it needs to strike first and from out of range of the Vanduul heavy weapons.