I used Armormech up until level 34 when I realised I never actually used anything I made. It was much easier to use orange armour and buy upgrades with commendations, and gave better results. I think you would end up doing the same with Armstech, except you would be able to make your own barrels instead of buying them. Cybertech seems useful for making upgrades and grenades (I think it's Cybertech that gets them anyway). I've started leveling Biotech for the reusable stims, augments, medpacks etc. It seems to me that only Armormech isn't really that great (apart from Synthweacving and Artificing of course), so just pick the one you like the products of most.