I have noticed that in Elemental there is always only one real way to go for armor - the most advanced one you have so long as you can afford to put it on your soldiers. My suggestion is to have several different branches of armor (I am going to give an example with 3 armor branches) that have varied defense bonuses, dodge penalties, and costs. I also think that there should be a higher base dodge rating but the dodge penalties for wearing armor should be heavier and shields should not provide a dodge bonus (at least not the large dodge bonus that shields currently provide - you're telling me that you react faster and move more quickly while you carry a big, heavy piece of wood/metal?).

Example (all numbers are made up off the top of my head):

1. Light Armor - low defense value for research level - possibly equivalent to armor two or three levels earlier in the tree for heavier armors; costs small amounts of materials and gold, generally less than equivalent research level heavier armors and possibly less than earlier heavier armors; only minor dodge penalties - I think dodge reduction of 0-1 for the whole set. These would be, as an example, leather/fur/padded armors, with small/medium wooden shields (i.e. wooden buckler, 'light wood shield,' wooden kite shield).
2. Medium Armor - moderate defense value for research level - possibly equivalent to armor one or two levels earlier in the tree from the heaviest armor type; costs moderate amounts materials and gold as well as small amounts of metal; has moderate dodge penalties for the set - perhaps a reduction of 1-2 dodge for the whole set. As an example, medium armors would be ring/chain/scale mail type armors, possibly heavier versions of light armor (i.e., 'reinforced/hardened' leather armor). with medium/large wooden or small/medium metal shields (i.e. wooden kite shield/tower shield, metal buckler/kite shield, 'light metal shield').
3. Heavy Armor - high defense value for research level, as good as or better than more advanced lighter armors; costs a lot of gold and metal, with some kind of materials cost in addition - no idea how much would be reasonable; big dodge penalties - dodge reduction of more than 3 for the whole set, with really heavy or cheap variants reducing dodge to 0 (heavy armor is supposed to absorb hits, therefore its tough but you're not going to be jumping around like a rabbit while you wear it). These armors would be various types of plate, possibly heavy versions of the medium armors, with large wooden and medium/large metal shields (i.e., wooden tower shields, metal kite and tower shields).

As far as differentiating various armors within the light/medium/heavy groupings,  you could go for something simple like "padded is better than nothing, fur is better than padded, leather is better than fur, ring mail better than fur, chain better than ring, scale better than chain, plate better than all of it" for defense ratings, or have subsets of each armor type that have a different balance of bonuses - i.e., padded gives no dodge penalties but has less defense than fur, fur gives dodge penalties of ~0.5 but has better defense than padded, leather gives dodge penalties of ~1 but has the best light armor defense rating, and call it 'wolf/bear/troll fur' 'cloth/cotton/??? padded' 'deer/wolf/bear leather' (this works better for me with metals - iron/steel/adamantium plate).

Also, you could implement a end-of-branch repeatable tech for each armor type. As an example:

1. Light Armor - 'Refined Light Armor' to provide small defense bonuses to Light Armors (~0.1 per piece), with moderate (~0.1) dodge bonuses per piece (as in the piece itself has (-x + 0.1*times_researched) dodge bonus).
2. Medium Armor - 'Refined Medium Armor' to provide moderate defense bonuses to Medium Armors (~0.5 per piece), with small (~0.05) dodge bonuses per piece (as in the piece itself has (-x + 0.05*times_researched) dodge bonus).
3. Heavy Armor - 'Refined Heavy Armor' to provide large defense bonuses to Heavy armors (~1 per piece), with either no or very small (~0.01) dodge bonuses per piece (as in the piece itself has (-x + 0.01*times_researched) dodge bonus).

Any numbers that I provided were scalars, not percentages, and you could also keep the 'Refined Defense' tech (+10% defense per time researched) - just make it require any two of the armor branches be researched up to a high level. You can also include 'master' versions of the various armors, or use the 'master' version as the ultimate heavy armor tech, or some such thing.

I also think that only enchanted armors should give dodge bonuses without some kind of high level research being done, and that shields should not grant dodge bonuses - carrying large pieces of material is useful for stopping blows, but it isn't going to improve your reaction time. The dodge bonuses that I suggested in the end-of-branch repeatable researches I view as more of training in how to move well in that type of armor than an actual bonus.