I'm currently grinding up through the line, (currently half way through the T4 Danae), so far my conclusion is;
You make a single mistake = dead/400 hp left praying no one finds you..
Read the situation wrong/island hop at the wrong time = dead.
I would be absolutely fine with this if they actually were a glass cannon.
Tactics?
Against Destroyers.
I have found them to not be destroyer hunters in the lower tiers.
The shells take so long to travel to the target that the Destroyer is able to turn away and dodge the incoming fire.
You have a chance of torpedoing them, however they have superior agility and a tighter turning circle, meaning they're more likely to dodge your torpedoes and land theirs on you.
Against Cruisers.
Very hit and miss engagements, usually die to fire. Or end up lit up by Battleships elsewhere seeing a spotted RNCL Free exp.
Against Battleships.
Tiers 1-4? Run, hide. Don't bother launching torpedoes unless they're blundering around a corner.
Slaloming and Angling does not work, you just get citadelled no matter what.
To summarise.
I wait at an island and hope an enemy makes a mistake where I can use torpedoes against them, killing them in a devastating strike - failing that limp away on extremely low health and find another island to hide behind.
I understand the concept of glass cannon with a high skill floor. I understand you are supposed to stealthily move around, However glass cannons should be able to apply damage well and fast! (Its part of the trade-off)
The damage from your guns in tier 1-4 is so awful I would rather take them off my damn ship and have more torpedo launchers.
To call these ships simply Cruisers is a misnomer. They are oversized Destroyers with only the benefit of fast acceleration/speed on turning.
I enjoy a challenge. I usually enjoy glass cannon builds in any game and the skill it takes to use them effectively, this is not the case as far as I have experienced so far. I hope once I reach the higher tiers (God help me with the Emerald by all accounts) that I will find that gameplay which I enjoy.