i took bengreenwood's advice and ditched the blocks in the face so now the model is down to 204 triangles, which is pretty low.
also, i wasn't happy with the messy uvmapping so i spent a while re-doing it from scratch. i wanted to get more detail in parts that would get more attention so i uvmapped the model with this grid texture that i've made...
...and started resizing the uvmapping. the grid texture makes it very easy to see where the detail is. in the end i ended up with this...
...with the bulk of the detail on the face and chestplate. also i put more detail into the upper body and arms than in the legs. i also mirrored the arms and legs so both sides share the same texture on the uvmap. this means the arms and legs are limited to being symmetrical, but that's ok for this particular model. this is what it looks like now i've baked the AO into the skin...
...i'm not actually doing anything with the extra detail i packed into the face and chestplate, but at least it's there if anyone wanted to re-skin it.