a) It's interesting to take a peek at the Micro Lutheran Denominations in Pastor Zip's enumeration. Lots of them are split off of the right edge, either in terms of things like women's voting privileges or kind of the liturgical/eccleisal right - ELDoNA comes to mind. Many of them seem to me to be one generation denominations - when this generation of pastors retires, who's going to replace them?
b) Which leads to Apostolic Succession. Here's the Wikipedia article on the topic, with much to check out when it comes to Lutherans -
https://en.wikipedia.org/wiki/Apostolic_succession. Since the Apostles' Teaching is what's historically been at the heart of it for Lutherans, it's kind of difficult to get wound up over the other point of view, which is biological and ontological. And yet many do. Certainly it's a distinctive for the RCC.
It's one of those inside out things where Lutherans tend to think of it as adiaphora and extra-biblical and those with it, who are accused to adding to the biblical record with (oh, no) the traditions of the church catholic through history point to the Biblical record. "You are Peter and upon this Rock" is right there in the Bible but we Lutherans interpret the Rock to be Apostolic Teaching based on his confession, even though the resultant gift of binding and loosing is given to Peter in the second person singular - that is to him personally - and not to all the disciples in that passage. Am I wrong there? That's the way it reads to me. So we take our reading off of "They continued steadfast in the apostles' teaching and fellowship" in Acts.
Ecclesiology. A soft spot, a weak spot, a chink in the Lutheran armor.
Dave Benke