Some large balance issues I have come across.
Masterwork Chain and Light Plate - This is pretty obviously unbalanced. Masterwork Chain only reduces initiative by 2, for 26 Defense. That's only 6 less defense then plate but 4 more initiative, OP. Meanwhile Light Plate grants 22 Defense and reduces Initiative by 6! Six! That's 4 less Initiative then chain for only 6 defense. Never ever get that, your units will be so slow they will never move.
Iron Golems - People have mentioned this many times before but Iron Golems are very Up. They are far more expensive and far worse then Juggernauts. One little thing that would fix them though is to just take all the traits like Immune to Criticals, Immune to Poison, and Vulnerable to Lightning and either add them together into one Golem trait or just add them to the basic unit. This would allow us to give Golems more then a single unit design trait and make them much better and unique.