The tech trees seem to be a well-intentioned system, albeit poorly implemented.
In the low tiers, players are forced to play either a destroyer (tank), artillery cruiser (damage), or tactical cruiser (healer). The benefit is that it allows new players to be introduced to one of the 3 "roles" within the game. However, it also locks players wanting to progress to specific classes behind other classes that they usually have no intention of playing. Or you could have what Wargaming uses (forcing new players to play [insert well-rounded tank/plane/ship here] before progressing to other lines). My suggestion would be to have tier 1 versions of every ship.
Progress into a specific class is exactly what players are not meant to do, they are meant to have a balanced fleet of five distincts roles/builds. That's 90% of the reason of existence of the tech tree.
Destroyers are no tanks at all. Actually the game doesn't work on the Triad.
Systematically placating a scheme coming from other games that is not this game's is half the problems that are felt in those fora and why devs don't bother to respond again and again, because there's no point. Furthermore to beta testers. It's a counter-point, beta testing the feelings is part of a beta test.
Also, you have all main classes on tier 2 that is really not far in the tech tree at all. Like two days into. I played lightly and unlocked fully all the tier 2 in a meager week.
Maintainance costs are designed to prevent bad players from entering the higher tiers, but also punish players for taking damage, a.k.a. not hiding cloaked in a corner.
As they are right now, they are meant for players to not only play in the highest tiers and populate the middle ones.