i'm a electrifying comm, so i need that tf. first 3 minutes of the game i only have 2 ips, and an electrified tf. without that ele'd tf, my base would be defenseless. But after that, i spread everything out, because if that lone skulk has enough time to come into your base and start chomping on your armory and obs, then its a sign that you're not pushing them hard enough, and that your most likely dead, and that stuffing your base into an area of 2m^2 isn't going to help it any further.
Mines are also not quite that good.
Armory (20, 25 res i think) + mines (10 res) gives you a quick 30 - 35 res defense against skulks. However, then you have armory humping which will kill the teamwork of the whole game. I find that once i build an armory, my team hardly listen to "PHASE THROUGH!" and "SAVE DOUBLE RES!". The only reason i build an armory at all is to dispense shotguns, and get armslab and obs.