Thank you for reviewing my map! I can tell that you spent quite a long time looking at all the details and I appreciate that. I'll go over the suggestions you made:
1. This was such a simple fix that I'm surprised I didn't catch it. It's fixed now. I'll update the map soon.
2. Also fixed.
3. I'll address this at suggestion 7.
4. I completely agree. Chaos damage is pretty powerful and so originally I had considered not putting this upgrade in. But after giving it some thought I really felt like Chaos damage is such an integral part of the Legion's identity that ultimately I decided to keep it in. I gated it by all the other upgrades as well as a long research time in order to ensure that the research was only capable during late-game.
5. I could try nerfing the duration little. The duration is short because I wanted the potion to be more of an emergency potion to give your hero a chance to get out of a bad situation.
6. To be perfectly honest, I'm not particularly satisfied with Execution and the Pit Lord's arsenal in general. I think the other heroes have more to offer so I'll be working to make the Pit Lord a more desirable choice.
7. I felt like 3 and 7 were pretty similar so I thought I'd answer them together. I understand that these spells are very simple and not the most exciting. A lot of these units actually had some more intricate spells but during the development process I just felt like it was a little too much and altogether way too flashy and complex. So I toned it down and simplified them to what they are now. While firebolt isn't anything new, it isn't used by any of the other 4 base races and I thought it fit the Eredar's arsenal. Sunder was just my way of making a Jailer form of Banish with its own icon and tool tip. It was my intention to give them Banish but I wanted to make it more fitting as Jailers manipulate the soul. So in all honestly, renaming it and changing its icon is purely meant for immersion.
8. I thought about doing this too. I couldn't figure out how to though as sentinel, as far as I know, is the only spell that has charges. If the Fel Mine is a little over-tuned I'll consider either nerfing the damage or increasing the cooldown.
9. I think the only magic resistances, are resistant skin, spell immunity, avatar and anti-magic potion (outside of triggers). Ascend and Descend is the main power of the Terrorguard but I felt it wasn't enough when you could easily build Felbats for anti-air and Wrathguards or Mo'Args for melee. Resistant Skin was meant to carve its own niche. It isn't the strongest ground unit or the best air but the combination of being both a ground and air unit and having innate resistances to certain spells makes it worth training.
10. I originally had it so it was 2 Dreadstalkers. Level 2 was Feedback and level 3 was Resistant skin. But then it ended up being exactly like Feral Spirit. I definitely liked the Mana Burn idea and thought about it myself. I was concerned it might be too much micro-management.
11. This is completely intended. I felt it would make for some interesting game play choices.
12. I could reduce the duration. I was thinking maybe it lasted for too long. Or I could remove the invisibility and increase its health slightly to compensate.
13. The gold and lumber cost remains the same and they can only attack air. You could choose to mass them but it won't get you very far in my opinion.
14. Well, when Berseker is researched, they are technically still troll headhunters, but they upgraded. Felguards cant evolve into Wrathguards, and Succubus can't evolve into Shivarra. As for Succubus and Shivarra not being melee. I felt that it was best to follow the other races (except night elves) where the first basic unit is melee and the second one is a non-caster ranged unit. Out, of all the demons, Succubus and Shivarra were the best candidates for that. I got the idea from WoW (I think it was MoP expansion), where the Succubus and Shivarra were ranged pets for the warlock, so I felt it would work.
15. The Dreadlord has a Fel Reaver

Jokes aside, Rain of Chaos was meant to be a spell used for ground units and Eradication Field was meant for air units. Also, the burning legion severely lacks aerial demons; only Felbats, Terrorguards/Doomguards, and Command Ships and I already have all of those covered. Well, there's also Aranasi but I haven't found anything for that but WoW Rips.
16. I reduced the selection time to 15 seconds. I think that shouldn't be too long.
Anyways, again I really do appreciate your review. I felt it was very fair and thorough. I will continue to work on the map and I hope you'll continue to play it! =)