Every class is available from T-2. Just do another tech tree. To say you want this SPECIFIC ship from this SPECIFIC line but it's at T-4 and that's BS is pretty ridiculous. There's no consequence to going up multiple lines at once, as long as you're not doing two of the same ship class from different lines (then you have to buy each module you want twice). You want healers but don't want to wait till T4 just to get the one (frankly overpowered) Akula ship? Play Oberon. You want destroyers but don't want to wait till T4 to get the Vindicta? Play Jupiter Arms. The differences between them are not massive. It's speed, health and primary weapon. If that's just waaaay too much to ask for you, then you might just be a bit too difficult to please.
Also, this whoooole progression system is still very new. Balance changes will be made constantly. Frankly, balance is very good given how fresh out of a major overhaul everything is. Ever played Tanks or War Thunder? This game's balancing is agodlike compared to either of those, and both of those are far older and have had far more time to adjust (point is Dreadnought does pretty well for balancing). The Dola (I don't have experience flying it but I see it more often than most ships at T3/4 so I doubt it's actually "simply frustrating and wasted" but that aside) might be bad now but if that's the case it will in all likelihood be adjusted soon.
Sidenote: I play the Fulgora all the time. It's my favourite ship so far and I do really well with it. It's pretty slow for a corvette but it's really strong when equipped with the right loadout. I use Blink Warp, Drain Torpedoes, Autoguns, and Afterburner. It might be the speed that other players have an issue with but I enjoy the ship a lot.