Those are slightly different issues.
The army getting truncated is because it exceeds the support cap - the support the majority race have for your policies. The remaining units are held in reserve and are available from structures you build on the map (they won't cost any time or resources to bring into the battle). It's intentional that your starting forces are limited, and a key gameplay element.
Your chances could be improved by being able to pick which units are deployed, but that's an entirely new feature - but an interesting one. I think I would like to be able to select which units and how many to deploy to get a good mix under the cap.
