Recently, I attacked a player and my gold tanks were killed. My gold troop count was also over the limit so I could not build my tanks back. There was no way to get my tanks back because you cannot "heal" mechanical troops (which is why I am hoping that this is the reason you cannot heal mechanical troops- it's not the right word to use).
This is why I am suggesting a "repair" function where dwarfs are able to repair their mech troops instead of healing them.
Think about it this way.. if another race were to attack someone their gold troops would get injured and they can heal. So if they were over the limit they can just heal their troops back. Another scenario to think about is if a lich user were to attack a dwarf user. Lich does very well against dwarfs so even if you are a dwarf and you win, chances are that you will lose some mech units and your opponent will still have their higher level troops to be able to heal and use again. So yes, Lich is overpowered against dwarf (which I have said a thousand times) and should be and needs to be fixed, tweaked, and repaired.
EDIT: I am not completely sure, however if you are over the cap and you heal gold units in your hospital you can go over the cap to where you originally started. Someone please comment down below if this is fact or fiction.
EDIT:Decreae power of spiders. Poison is not meant to kill in 2 shots.
(If I have stated anything incorrectly, someone please correct me down below.)