If I understand you correctly; the starting armies are only useful for 'rush' tactics. If you fail to rush (new player, slow to move - whatever) then the game quickly reverts to standard rts with the starting armies adding almost nothing (i might be mistaken but even at 1:3 it sounds like a very small # for a long running battle). I.e, it sounds like if you can't complete the rts battle in a short period then the starting armies are no longer relevant and it doesn't matter if the initial armies are 1 vs 1 or 1 vs 10 (esp if the person with a single army has a lot of upgrades they can apply to the armies they build on the battle map).
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I'm sure Stabbey has done some analysis here (his other posts are quite detailed with the things he has tried) so perhaps you could provide further insight.
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If what I said is correct I think there is something else amiss here in the game mechanics. There should be a clear advantage to a large starting army (perhaps it could impact the size of the army you can build or the number of citizens you can recruit for building armies) beyond an initial rush tactic.

(of course I say this because I always sucked at rush tactics frown )