Not yet run in to any Coursers. I've barely played through the main storyline ( only just saving Valentine ! ) as i've been building up settlements.

For me personally I use any armor pieces I find to make me more protected. It doesn't matter for me what set. But do remember that modding armor pieces ages a huge defense difference and weight in armor. Majority of people prefer power armor as it is OP as hell. But fusion cores cost too much and scavenging for junk to repair parts will take too long.

https://pbs.twimg.com/media/CVDJEC6UwAAPRJD.jpg. It offers all the protection of tissue paper but for the sake of looking good, it's a price I'm happy to pay.

My first character didn't even know about the tiers. The 'Sturdy' and 'Heavy' is generally replaced with a mod name and even when I saw one that said Sturdy I just assumed it was a mod and paid it no mind. Now on my current character I have her in full suit of Shadowed Sturdy Leather Armor with a insulated Vault Suit underneath. Love'n the look.