It's all about cost vs benefit in dust. Often the only reason to get level four or five in a skill is to have the passive bonus help lower level versions of the item. A proto logi suit might cost me 100-130k a pop. I"ll have 4 equipment slots and some where between 300 shields and 500-700 armor. I'll still die in a few seconds to most snipers, railguns or simply being run over by a LAV.
On the other hand you can still very competive with a advanced logistic suit. Have 3 equipment slots and mayve 200 shields and 300-400 armor. The over all cost is usually 20-40k but you can die 5-8 times as much for the price of a single proto suit. Heck you can even be pretty effective with a basic suit, you might have tissue paper for armor but you'll still have all the equipment and weapons that you need.
Sadly unless your a red zone or roof top sniper, defenses don't mean a lot in Dust. Complex shield and armor mods might buy you a few extra seconds of life against a single enemy but you'll still be pasted against a vehicle or concentrated fire from a few guys. Dust is a very offensive game. Slap a proto level weapon on a milta suit and it's almost as good as anything less than proto lol.
"That is not just scraping the bottom of the barrel, that is lifting the barrel up and poking some of the slimy sludge growing underneath the barrel."