I would just naturally level up your buildings, always keep your builders working and you will eventually get the sixth base (No need to spend gems and hurry the process). It is nice to have, but at your current might and hero levels, you are good with your five. As for inflated might: if you can raid with no issues, then your might is fine. There will come a point when you will need to start boosting might (the rewards are to nice not too).
This is just my personal opinion, but I would replace the enlighten talents whenever you get something better. For me, I only throw a high enlighten on a dupe for might or for a newly rolled hero I am trying to catch up to my main 6. The revive is a great talent for both druid or vlad, so that one is up to you.
For dungeons I would do whichever one you can easily farm without losing heroes that you can do at a reasonable speed.
4a. For the insciptions it's your personal choice how you get them up, as long as the end outcome is getting your main heroes to 80. Don't start inscripting past 80 until all of your heroes are 80 as you will start to starve yourself of blue crystals. I think I leveled all of mine up by multiples of ten, so I got everyone to 20, then everyone to 30, etc.. but, again, that's a preference.
4b. Originally when it came out everyone said keep your mines low and save the reds for combining, but at the point I am at I am in desperate need for blue crystals and I have started dumping my red crystals into my mines. That's what I do, someone else may have a better suggestion at your might.
4c. When you are at low level might and a low level LR your altars seem to never be touched. But you are going to hit a certain point where you are constantly fighting for your altars (I think I was around 50k might and lvl 12 LR?). Up until then my altars were never even touched. So I wouldn't worry about a zero defense, once you level might and LR it will change.
Hope this helps.