[Aleph]

I'm definitely not extensively experienced in Mictlan, but I like them as much as I like any nation in the game (most enjoyment thus far - Yomi, EA/LA Mictlan, MA/LA Ermor, LA Rl'yeh).

1. I tried to cover this above in the "bloodhunters of mictlan are cheaper but mictlan needs to spend blood in dominion maintenance" point. Not saying that mictlan spends 1/3 of its blood in dominion maintenance, but I've often spent 30+ slaves in sacrifice a round in 150 province games.
2. Lanka can easily forge knives, and if they want to sacrifice then level 2 priests with jade knives in temples that do spread dominion are pretty much the same as level 3 priests in non-functional temples.
3. See point 5.
4. Mictlan national summons do rock - I love the Tlahuelpuchi and Civeteto as assassins and leader/reanimators respective, and the Onaqui is great. So do Lanka's summons, however, albeit benefitting more from defensive than offensive blesses. And Lankan high end summons are remarkably good SCs, able to cast Mistform and Mirror Image, being sacred, and one possessing Blood Vengeance while the other automatically shrouds the battlefield in Darkness while possessing a fatiguing aura. I've taken out 100+ unit armies with a single Dakini with a snake ring, snake bladder stick, horned helm, and vine shield (funded by an early game mother oak, in turn funded by an early game push to skull mentors - an option that Mictlan generally lacks unless they get lucky with their national hero, since your pretender will likely be imprisoned for the best bless).
5. I made a similar point above re: Mictlan's magic being in general more predictable, but this particular example doesn't hold water. Armor of Thorns requires a little more luck, but it's definitely doable. All it takes is a bramble mace (forged by a Yogini, guaranteed nature 2) and either a lucky BBB Rakshasi or an empowered BB Rakshasi (not particularly rare, roughly 50% of all Rakshasi are at least BB), which is the same thing you do with Priest Kings. Then your assembly line is up and rolling, and the random picks which were annoying in fact now potentially give you anywhere from N4 to B4 with Armor of Thorns alone, without empowering or further items.
6-8. Lanka's national rank and file summons are pretty heavy brawlers and can do quite well all the way up, and their B6 national is a flying AAABBBDHH with Blood Vengeance for 50 blood. I'm not saying that Ice Devils wouldn't be nice on top of that, but I didn't really miss them and wouldn't use many of them in preference to the Dakini.
9. I think you're overestimating the difficulty this causes - it has pros and cons, like everything. But since they can get past the Armor of Thorns/Brazen Vessel/Blood Thorn horizon without any real difficulty, it's not a stumbling block on their road to blood dominance.

I want Mictlan to be the best at blood, and I'm certainly not super experienced in either nation. Initially, however, Lanka seems like it has too much blood power for the other things it has.