DPS as a single metric is often the only one considered in most discussions - but you are so right - balance is a MUCH wider subject .
You have to look at the resource investment (not just mass) to arrive at, not only that DPS, but the associated HP and mobility factors that go with it. Range and AOE should also represent major modifiers to DPS cost - it takes more resources to fashion a longer ranged weapon - and more again to have a weapon that can affect an area - the bigger the area - the more resource costly that should be (especially with the linear AOE in this game).
Platform matters - and basic motivation should affect valuations - hovercraft for example, have versatility - but acceleration and inertial issues. Submersible units would require substantial reinforcement over a non-submersible unit, etc. Tanks have a mobility advantage over walkers in some circumstances, but are at a disadvantage in others - those are just some aspects to consider.
Having done that across a group of roughly comparable units - you need to examine those metrics - and put them in relation to other classes. For example, are air units performing better, or worse, in those respects - is this the fundamental reason that air dominates the game ? Are they getting a free pass in relation to everything else ?
You cannot boil it down to anecdotal observation, if the basis is not quantifiable - then neither will be the results.