I mean on the battle map it is very difficult and takes many many turns before you can assemble a decent and balanced army that is versatile and have a army whose units can combine its arms to support itself.
THAT is the whole problem! As you say, it is difficult and very expensive to create a good army on the TBS map - and it is just frustrating to see it destroyed in no time on the RTS map because spamming of the units is made so incredibly cheap during the battle. Why should I then bother at all with the unit production on the TBS map? If I do not want to autoresolve (which is the only option at the moment where the winning chance does really count) but enter the combat as a dragon, I can just forget about assembling an army on the TBS map since the need for it is entirely obviated on the RTS map.
This is the balance issue which I have been talking about. There are surely different approaches to solve this problem: mine is to reduce the population size, yours is to increase the production and to lower the costs for the TBS units. At the end, both solutions have the same effect.
