Balin does have a low amount of health, but I think that is balanced out by how strong every other hero is, and how many summon heroes you can get, and also being able to get Mithril.
Anyways, I would like to make a proposal concerning the Mithril Shirts for heroes. Because of the limit on how many Dwarven Khazad-dum Veterans you can have at one time(which is 3), it is hard to get your heroes Mithril. To get all your heroes Mithril, you have to kill off some of your Veterans. Now this isn't much of a problem for Erebor, becuase they only have 4 heroes who can get Mithril (because Nori gets it automatically once he reaches level 10), but for Iron Hills with 5 heroes, and Ered Luin with 7 heroes, this is more of a problem. I don't think people should be sacrificing their heroic units to improve their heroes.
So my suggestion is that Veterans have a cooldown on their Mithril Shirt Ability. The cooldown will be extremely long (say 8 mins or so), but this means that you will not have to kill them to get more Mithril Shirts.
Now Ered Luin would still have to wait a long time to get all their heroes Mithril Shirts, so I have a suggestion for them. I think Bilbo should get his Mithril Shirt automatically once Thorin Oakenshield is recruited. Not only does this make sense in terms of lore (or at leas I'd assume so, it's shown in the Hobbit Movies and Mentioned in the Lord of the Rings movies), but it would make 1 less hero to give Mithril too. Bilbo is usually the last person you should give mithril too because the other heroes need it more, so this would make it easier for every hero to get Mithril.
I would like to hear opinion on these suggestions.
Greetings, Hamanathnath