QUOTE(TheCheshireKhajiit @ Dec 19 2016, 06:42 PM)

So does anyone here ever put points in a second armor class and mix and match armors from different classes? Or is that generally considered a bad idea?
Yes. If you read the varying armor passives carefully, you'll see some passives help for each piece while some only help if you wear at least 5 of the same kind. Additionally, one of the high end passives for the Undaunted skills gives you some incentive to wear at least one of each kind.
Now, based on all that, most players wear at least 5 of their primary armor type. Some do that as 5/1/1, others as 5/2, as 6/1, and some others stay with simply 7.
Buffy, for example wears 6 light and 1 heavy (hidden helm). The helm not only boasts a lot more armor than its light counterpart, she puts points in the first 3 heavy passives which all help her health. Her light passives are all about magicka. She doesn't care (much) about stamina so the medium bonuses are not as valuable to her as another light piece. She doesn't really expect to go for those high end Undaunted passives and even if she did, the advantages are not dramatic.
Know also that armor 'big' pieces (head, chest, legs, shield) give you more effect from whatever they are enchanted with than the same glyph places on a 'small' piece of armor (hands, feet, shoulders, belt). Following that logic, many players trait their big pieces with infused to exploit the extra enchantment enhancement, preferring to boost their Mundus Stone (via the Divine trait) on their smaller pieces. That is probably sound advice for most builds. Those who worship critical hit % (stamsorcs for example) though, will often trait Divine on all armor. Best to have a basic understanding of why folks tend to do what they do, then analyze it against your own build/play style.