The metal and crystal cost for troops are all outrageous to me.  It makes fielding more than a handful of armored troops nearly impossible, and they are easily destroyed by a Juggernaut, or magic, or magic staff troops.  I would actually love that you could only field a few troops in steel armor, if they weren't so easily destroyed.

Is it worth it?  I don't think so.  Maybe if you were able to level that unit up a lot, but the cost vs fragility of the unit, not really worth it.

Check out my mod on the armor redux.  I know its not perfect yet, it still needs some polish but I addressed this to a degree by making a crystal armor with the same cost of crystal as metal and champion's armor has a reduced crystal cost but it also now takes metal.

I like to rush for Ironworks, so I pretty much can never run out of metal... but crystal costs tend to hurt. I usually have 2 designs of most troops, a "normal" version that minimizes crystal costs that I use in most places to save crystal... and a final "enchanted" version for my SoD, but even these never use champion armor (main crystal costs comes from accessories).