What kind of diversity are you looking for? This was mostly beat to death in beta, but Ironclad wanted diversity in play style more than diversity of unit types - so all races have ships that fill the same basic roles, but with the varying research and abilities all three races play quite differently.

Entrenchment is adding more to it, the starbases and mine fields will be unique to each race.

They're not quite 1-to-1 matches once their abilities come into play. The Vasari light frigates can self-repair, Advent steal antimatter and spread it around their own fleets. Advent Illuminators create copies of themselves so the real frigate is harder to destroy, Vasari ones can bypass shields and become stationary to greatly increase their range, and TEC ones get AoE damage.. so on so forth

So yes, if you just look at the stats the ships are variations of the other races' counterparts (some more extreme than others), it's really the abilities that add diversity.

Basic stats and roles of the craft are fairly similar.  In multiplayer, tech levels needed make a large difference, and in general, the abilities make a fairly large difference too.

As an example, IF I use Vasari light frigates, I will ALWAYS get their repair ability, since it can turn the tide of a battle.  Vasari light frigates are ships to be preserved early game.   Advent light frigates are things you throw away more easily.  Their power is nice, but not devastating on it's own, and their role for me is more often than not filler if my crystal is short and little more.  Same basic role, but they get used (at least by me) in completely different ways.