Devices are extremely important! Consider putting a lot more focus on the devices, rather than just pursuing new brobots and planes, and upgrading them.
To give you an idea, consider a Laserbite, with Rank SS and Level 140, to a Sparrow, with Rank B and Level 20.
Only looking at the planes, Laserbite has armor 2 061 and power 673, where Sparrow has armor 633 and power 136. The Sparrow thus only has 31 % of the armor and 20 % of the power, compared to the Laserbite.
But the numbers look completely different if you equip Purple level IV equipment to both planes. Laserbite goes to armor 5 106 and power 1 204. Sparrow goes to armor 3 679, and power 667. The Sparrow now has 72 % of the armor, and 55 % of the power of the Laserbite.
This shows how important devices are, so go put a lot of effort developing devices.
The good thing with devices is also that an improvement there, will affect all your planes. When you upgrade a plane, well then only that plane got better.